(window.webpackJsonp=window.webpackJsonp||[]).push([[1674],{2085:function(t,a,s){"use strict";s.r(a);var n=s(31),e=Object(n.a)({},(function(){var t=this,a=t.$createElement,s=t._self._c||a;return s("ContentSlotsDistributor",{attrs:{"slot-key":t.$parent.slotKey}},[s("h1",{attrs:{id:"streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#streams"}},[t._v("#")]),t._v(" Streams")]),t._v(" "),s("p",[t._v("A "),s("code",[t._v("Stream")]),t._v(" represents a sequence of elements and supports different kind of operations to perform computations upon those elements. With Java 8, "),s("code",[t._v("Collection")]),t._v(" interface has two methods to generate a "),s("code",[t._v("Stream")]),t._v(": "),s("code",[t._v("stream()")]),t._v(" and "),s("code",[t._v("parallelStream()")]),t._v(". "),s("code",[t._v("Stream")]),t._v(" operations are either intermediate or terminal. Intermediate operations return a "),s("code",[t._v("Stream")]),t._v(" so multiple intermediate operations can be chained before the "),s("code",[t._v("Stream")]),t._v(" is closed. Terminal operations are either void or return a non-stream result.")]),t._v(" "),s("h2",{attrs:{id:"using-streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#using-streams"}},[t._v("#")]),t._v(" Using Streams")]),t._v(" "),s("p",[t._v("A "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream")]),s("OutboundLink")],1),t._v(" is a sequence of elements upon which sequential and parallel aggregate operations can be performed. Any given "),s("code",[t._v("Stream")]),t._v(" can potentially have an unlimited amount of data flowing through it. As a result, data received from a "),s("code",[t._v("Stream")]),t._v(" is processed individually as it arrives, as opposed to performing batch processing on the data altogether. When combined with "),s("a",{attrs:{href:"https://stackoverflow.com/documentation/java/91/lambda-expressions",target:"_blank",rel:"noopener noreferrer"}},[t._v("lambda expressions"),s("OutboundLink")],1),t._v(" they provide a concise way to perform operations on sequences of data using a functional approach.")]),t._v(" "),s("p",[s("strong",[t._v("Example:")]),t._v(" ("),s("a",{attrs:{href:"https://ideone.com/IUWRdv",target:"_blank",rel:"noopener noreferrer"}},[t._v("see it work on Ideone"),s("OutboundLink")],1),t._v(")")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" fruitStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"apple"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"banana"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"pear"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"kiwi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"orange"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\nfruitStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("contains")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"a"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toUpperCase")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[s("strong",[t._v("Output:")])]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("APPLE"),s("br"),t._v("\nBANANA"),s("br"),t._v("\nORANGE"),s("br"),t._v("\nPEAR")]),t._v(" "),s("p",[t._v("The operations performed by the above code can be summarized as follows:")]),t._v(" "),s("li",[t._v("\nCreate a `Stream"),s("String",[t._v("` containing a sequenced ordered [`Stream`](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html) of fruit `String` elements using the static factory method [`Stream.of(values)`](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#of-T...-).\n")])],1),t._v(" "),s("li",[t._v('\nThe [`filter()`](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#filter-java.util.function.Predicate-) operation retains only elements that match a given predicate (the elements that when tested by the predicate return true). In this case, it retains the elements containing an `"a"`. The predicate is given as a [lambda expression](https://stackoverflow.com/documentation/java/91/lambda-expressions).\n')]),t._v(" "),s("li",[t._v("\nThe [`map()`](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#map-java.util.function.Function-) operation transforms each element using a given function, called a mapper. In this case, each fruit `String` is mapped to its uppercase `String` version using the [method-reference](https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html) [`String::toUppercase`](https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#toUpperCase--).\n"),s("blockquote",[s("p",[t._v("**Note** that the `map()` operation will return a stream with a different generic type if the mapping function returns a type\ndifferent to its input parameter. For example on a `Stream"),s("String",[t._v("`\ncalling `.map(String::isEmpty)` returns a `Stream"),s("Boolean",[t._v("`")])],1)],1)])]),t._v(" "),s("li",[t._v("\nThe [`sorted()`](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#sorted--) operation sorts the elements of the `Stream` according to their natural ordering (lexicographically, in the case of `String`).\n")]),t._v(" "),s("li",[t._v("\nFinally, the [`forEach(action)`](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#forEach-java.util.function.Consumer-) operation performs an action which acts on each element of the `Stream`, passing it to a [Consumer](https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#sorted-java.util.Comparator-). In the example, each element is simply being printed to the console. This operation is a terminal operation, thus making it impossible to operate on it again.\n"),s("blockquote",[t._v("\n**Note** that operations defined on the `Stream` are performed **because** of the terminal operation. Without a terminal operation, the stream is not processed. Streams can not be reused. Once a terminal operation is called, the `Stream` object becomes unusable.\n")])]),t._v(" "),s("blockquote"),t._v(" "),s("p",[s("strong",[t._v("Note")]),t._v(" that operations defined on the "),s("code",[t._v("Stream")]),t._v(" are performed "),s("strong",[t._v("because")]),t._v(" of the terminal operation. Without a terminal operation, the stream is not processed. Streams can not be reused. Once a terminal operation is called, the "),s("code",[t._v("Stream")]),t._v(" object becomes unusable.")]),t._v(" "),s("p",[s("a",{attrs:{href:"https://i.stack.imgur.com/6p8aM.png",target:"_blank",rel:"noopener noreferrer"}},[s("img",{attrs:{src:"https://i.stack.imgur.com/6p8aM.png",alt:"Chained operations"}}),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("Operations (as seen above) are chained together to form what can be seen as a query on the data.")]),t._v(" "),s("h3",{attrs:{id:"closing-streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#closing-streams"}},[t._v("#")]),t._v(" Closing Streams")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[s("strong",[t._v("Note that a "),s("code",[t._v("Stream")]),t._v(" generally does not have to be closed.")]),t._v(" It is only required to close streams that operate on IO channels. Most "),s("code",[t._v("Stream")]),t._v(" types don't operate on resources and therefore don't require closing.")]),t._v(" "),s("p",[t._v("The "),s("code",[t._v("Stream")]),t._v(" interface extends "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/lang/AutoCloseable.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("AutoCloseable")]),s("OutboundLink")],1),t._v(". Streams can be closed by calling the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/lang/AutoCloseable.html#close--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("close")]),s("OutboundLink")],1),t._v(" method or by using  try-with-resource statements.")]),t._v(" "),s("p",[t._v("An example use case where a "),s("code",[t._v("Stream")]),t._v(" should be closed is when you create a "),s("code",[t._v("Stream")]),t._v(" of lines from a file:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("try")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" lines "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Files")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("lines")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Paths")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("get")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"somePath"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    lines"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("The "),s("code",[t._v("Stream")]),t._v(" interface also declares the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/BaseStream.html#onClose-java.lang.Runnable-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream.onClose()")]),s("OutboundLink")],1),t._v(" method which allows you to register "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/lang/Runnable.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Runnable")]),s("OutboundLink")],1),t._v(" handlers which will be called when the stream is closed. An example use case is where code which produces a stream needs to know when it is consumed to perform some cleanup.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("streamAndDelete")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Path")]),t._v(" path"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("throws")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IOException")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Files")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("lines")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("path"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("onClose")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" someClass"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("deletePath")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("path"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("The run handler will only execute if the "),s("code",[t._v("close()")]),t._v(" method gets called, either explicitly or implicitly by a try-with-resources statement.")]),t._v(" "),s("h3",{attrs:{id:"processing-order"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#processing-order"}},[t._v("#")]),t._v(" Processing Order")]),t._v(" "),s("p",[t._v("A "),s("code",[t._v("Stream")]),t._v(" object's processing can be sequential or "),s("a",{attrs:{href:"http://stackoverflow.com/documentation/java/88/streams/2785/parallel-stream#t=201607281158351104612",target:"_blank",rel:"noopener noreferrer"}},[t._v("parallel"),s("OutboundLink")],1),t._v(".")]),t._v(" "),s("p",[t._v("In a "),s("strong",[t._v("sequential")]),t._v(" mode, the elements are processed in the order of the source of the "),s("code",[t._v("Stream")]),t._v(". If the "),s("code",[t._v("Stream")]),t._v(" is ordered (such as a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/SortedMap.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("SortedMap")]),s("OutboundLink")],1),t._v(" implementation or a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/List.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("List")]),s("OutboundLink")],1),t._v(") the processing is guaranteed to match the ordering of the source. In other cases, however, care should be taken not to depend on the ordering (see: "),s("a",{attrs:{href:"http://stackoverflow.com/q/1882762/1667004",target:"_blank",rel:"noopener noreferrer"}},[t._v("is the Java "),s("code",[t._v("HashMap")]),t._v(" "),s("code",[t._v("keySet()")]),t._v(" iteration order consistent?"),s("OutboundLink")],1),t._v(").")]),t._v(" "),s("p",[s("strong",[t._v("Example:")])]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" integerList "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("42")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" \n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// sequential ")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("long")]),t._v(" howManyOddNumbers "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" integerList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                                    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("e "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("e "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("%")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("==")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                                    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("count")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" \n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("howManyOddNumbers"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Output: 2")]),t._v("\n\n")])])]),s("p",[s("a",{attrs:{href:"https://ideone.com/FuMz1c",target:"_blank",rel:"noopener noreferrer"}},[t._v("Live on Ideone"),s("OutboundLink")],1)]),t._v(" "),s("p",[s("strong",[t._v("Parallel")]),t._v(" mode allows the use of multiple threads on multiple cores but there is no guarantee of the order in which elements are processed.")]),t._v(" "),s("p",[t._v("If multiple methods are called on a sequential "),s("code",[t._v("Stream")]),t._v(", not every method has to be invoked. For example, if a "),s("code",[t._v("Stream")]),t._v(" is filtered and the number of elements is reduced to one, a subsequent call to a method such as "),s("code",[t._v("sort")]),t._v(" will not occur. This can increase the performance of a sequential "),s("code",[t._v("Stream")]),t._v(" — an optimization that is not possible with a parallel "),s("code",[t._v("Stream")]),t._v(".")]),t._v(" "),s("p",[s("strong",[t._v("Example:")])]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// parallel")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("long")]),t._v(" howManyOddNumbersParallel "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" integerList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("parallelStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                                            "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("e "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("e "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("%")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("==")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                                            "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("count")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("howManyOddNumbersParallel"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Output: 2")]),t._v("\n\n")])])]),s("p",[s("a",{attrs:{href:"https://ideone.com/FuMz1c",target:"_blank",rel:"noopener noreferrer"}},[t._v("Live on Ideone"),s("OutboundLink")],1)]),t._v(" "),s("h3",{attrs:{id:"differences-from-containers-or-collections"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#differences-from-containers-or-collections"}},[t._v("#")]),t._v(" Differences from Containers (or "),s("a",{attrs:{href:"https://stackoverflow.com/documentation/java/90/collections",target:"_blank",rel:"noopener noreferrer"}},[t._v("Collections"),s("OutboundLink")],1),t._v(")")]),t._v(" "),s("p",[t._v("While some actions can be performed on both Containers and Streams, they ultimately serve different purposes and support different operations. Containers are more focused on how the elements are stored and how those elements can be accessed efficiently. A "),s("code",[t._v("Stream")]),t._v(", on the other hand, doesn't provide direct access and manipulation to its elements; it is more dedicated to the group of objects as a collective entity and performing operations on that entity as a whole. "),s("code",[t._v("Stream")]),t._v(" and "),s("code",[t._v("Collection")]),t._v(" are separate high-level abstractions for these differing purposes.")]),t._v(" "),s("h2",{attrs:{id:"consuming-streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#consuming-streams"}},[t._v("#")]),t._v(" Consuming Streams")]),t._v(" "),s("p",[t._v("A "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream")]),s("OutboundLink")],1),t._v(" will only be traversed when there is a "),s("strong",[t._v("terminal operation")]),t._v(", like "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#count--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("count()")]),s("OutboundLink")],1),t._v(", "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#collect-java.util.stream.Collector-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("collect()")]),s("OutboundLink")],1),t._v(" or "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#forEach-java.util.function.Consumer-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("forEach()")]),s("OutboundLink")],1),t._v(". Otherwise, no operation on the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream")]),s("OutboundLink")],1),t._v(" will be performed.")]),t._v(" "),s("p",[t._v("In the following example, no terminal operation is added to the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream")]),s("OutboundLink")],1),t._v(", so the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#filter-java.util.function.Predicate-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("filter()")]),s("OutboundLink")],1),t._v(" operation will not be invoked and no output will be produced because "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#peek-java.util.function.Consumer-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("peek()")]),s("OutboundLink")],1),t._v(" is NOT a "),s("strong",[t._v("terminal operation")]),t._v(".")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("range")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("a "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" a "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("%")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("==")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("peek")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[s("a",{attrs:{href:"https://ideone.com/YDijRj",target:"_blank",rel:"noopener noreferrer"}},[t._v("Live on Ideone"),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("This is a "),s("code",[t._v("Stream")]),t._v(" sequence with a valid "),s("strong",[t._v("terminal operation")]),t._v(", thus an output is produced.")]),t._v(" "),s("p",[t._v("You could also use "),s("code",[t._v("forEach")]),t._v(" instead of "),s("code",[t._v("peek")]),t._v(":")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("range")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("a "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" a "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("%")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("==")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" \n\n")])])]),s("p",[s("a",{attrs:{href:"https://ideone.com/LzUoM6",target:"_blank",rel:"noopener noreferrer"}},[t._v("Live on Ideone"),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("Output:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("2"),s("br"),t._v("\n4"),s("br"),t._v("\n6"),s("br"),t._v("\n8")]),t._v(" "),s("p",[t._v("After the terminal operation is performed, the "),s("code",[t._v("Stream")]),t._v(" is consumed and cannot be reused.")]),t._v(" "),s("p",[t._v("Although a given stream object cannot be reused, it's easy to create a reusable "),s("code",[t._v("Iterable")]),t._v(" that delegates to a stream pipeline. This can be useful for returning a modified view of a live data set without having to collect results into a temporary structure.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"FOO"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"BAR"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Iterable")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" iterable "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" list"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toLowerCase")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("iterator")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("for")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" str "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" iterable"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("str"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("for")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" str "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" iterable"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("str"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("Output:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("foo"),s("br"),t._v("\nbar"),s("br"),t._v("\nfoo"),s("br"),t._v("\nbar"),s("br")]),t._v(" "),s("p",[t._v("This works because "),s("code",[t._v("Iterable")]),t._v(" declares a single abstract method "),s("code",[t._v("Iterator<T> iterator()")]),t._v(". That makes it effectively a functional interface, implemented by a lambda that creates a new stream on each call.")]),t._v(" "),s("p",[t._v("In general, a "),s("code",[t._v("Stream")]),t._v(" operates as shown in the following image:")]),t._v(" "),s("h3",{attrs:{id:""}},[s("a",{staticClass:"header-anchor",attrs:{href:"#"}},[t._v("#")]),t._v(" "),s("a",{attrs:{href:"https://i.stack.imgur.com/lrwjM.jpg",target:"_blank",rel:"noopener noreferrer"}},[s("img",{attrs:{src:"https://i.stack.imgur.com/lrwjM.jpg",alt:"Stream Operation"}}),s("OutboundLink")],1)]),t._v(" "),s("p",[s("strong",[t._v("NOTE")]),t._v(": Argument checks are always performed, even without a "),s("strong",[t._v("terminal operation")]),t._v(":")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("try")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("range")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("null")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("catch")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("NullPointerException")]),t._v(" e"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"We got a NullPointerException as null was passed as an argument to filter()"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[s("a",{attrs:{href:"https://ideone.com/zrkoRz",target:"_blank",rel:"noopener noreferrer"}},[t._v("Live on Ideone"),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("Output:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("We got a NullPointerException as null was passed as an argument to filter()")]),t._v(" "),s("h2",{attrs:{id:"creating-a-frequency-map"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#creating-a-frequency-map"}},[t._v("#")]),t._v(" Creating a Frequency Map")]),t._v(" "),s("p",[t._v("The "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#groupingBy-java.util.function.Function-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("groupingBy(classifier, downstream)")]),s("OutboundLink")],1),t._v(" collector allows the collection of "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream")]),s("OutboundLink")],1),t._v(" elements into a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Map.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Map")]),s("OutboundLink")],1),t._v(" by classifying each element in a group and performing a downstream operation on the elements classified in the same group.")]),t._v(" "),s("p",[t._v("A classic example of this principle is to use a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Map.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Map")]),s("OutboundLink")],1),t._v(" to count the occurrences of elements in a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream")]),s("OutboundLink")],1),t._v(". In this example, the classifier is simply the identity function, which returns the element as-is. The downstream operation counts the number of equal elements, using "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#counting--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("counting()")]),s("OutboundLink")],1),t._v(".")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"apple"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"orange"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"banana"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"apple"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n      "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("groupingBy")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Function")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("identity")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("counting")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n      "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("entrySet")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n      "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("The downstream operation is itself a collector ("),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#counting--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Collectors.counting()")]),s("OutboundLink")],1),t._v(") that operates on elements of type String and produces a result of type "),s("code",[t._v("Long")]),t._v(". The result of the "),s("code",[t._v("collect")]),t._v(" method call is a "),s("code",[t._v("Map<String, Long>")]),t._v(".")]),t._v(" "),s("p",[t._v("This would produce the following output:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("banana=1"),s("br"),t._v("\norange=1"),s("br"),t._v("\napple=2")]),t._v(" "),s("h2",{attrs:{id:"infinite-streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#infinite-streams"}},[t._v("#")]),t._v(" Infinite Streams")]),t._v(" "),s("p",[t._v("It is possible to generate a "),s("code",[t._v("Stream")]),t._v(" that does not end. Calling a terminal method on an infinite "),s("code",[t._v("Stream")]),t._v(" causes the "),s("code",[t._v("Stream")]),t._v(" to enter an infinite loop. The "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#limit-long-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("limit")]),s("OutboundLink")],1),t._v(" method of a "),s("code",[t._v("Stream")]),t._v(" can be used to limit the number of terms of the "),s("code",[t._v("Stream")]),t._v(" that Java processes.")]),t._v(" "),s("p",[t._v("This example generates a "),s("code",[t._v("Stream")]),t._v(" of all natural numbers, starting with the number 1. Each successive term of the "),s("code",[t._v("Stream")]),t._v(" is one higher than the previous. By calling the limit method of this "),s("code",[t._v("Stream")]),t._v(", only the first five terms of the "),s("code",[t._v("Stream")]),t._v(" are considered and printed.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Generate infinite stream - 1, 2, 3, 4, 5, 6, 7, ...")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),t._v(" naturalNumbers "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("iterate")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" x "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" x "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Print out only the first 5 terms")]),t._v("\nnaturalNumbers"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("limit")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Output:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("1"),s("br"),t._v("\n2"),s("br"),t._v("\n3"),s("br"),t._v("\n4"),s("br"),t._v("\n5")]),t._v(" "),s("p",[t._v("Another way of generating an infinite stream is using the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#generate-java.util.function.Supplier-",target:"_blank",rel:"noopener noreferrer"}},[t._v("Stream.generate"),s("OutboundLink")],1),t._v(" method. This method takes a "),s("a",{attrs:{href:"https://stackoverflow.com/documentation/java/91/lambda-expressions",target:"_blank",rel:"noopener noreferrer"}},[t._v("lambda"),s("OutboundLink")],1),t._v(" of type "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/function/Supplier.html",target:"_blank",rel:"noopener noreferrer"}},[t._v("Supplier"),s("OutboundLink")],1),t._v(".")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Generate an infinite stream of random numbers")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Double")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" infiniteRandomNumbers "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("generate")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Math")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("random")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Print out only the first 10 random numbers")]),t._v("\ninfiniteRandomNumbers"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("limit")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"collect-elements-of-a-stream-into-a-collection"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#collect-elements-of-a-stream-into-a-collection"}},[t._v("#")]),t._v(" Collect Elements of a Stream into a Collection")]),t._v(" "),s("h3",{attrs:{id:"collect-with-tolist-and-toset"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#collect-with-tolist-and-toset"}},[t._v("#")]),t._v(" Collect with "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#toList--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("toList()")]),s("OutboundLink")],1),t._v(" and "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#toSet--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("toSet()")]),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("Elements from a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream")]),s("OutboundLink")],1),t._v(" can be easily collected into a container by using the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#collect-java.util.stream.Collector-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream.collect")]),s("OutboundLink")],1),t._v(" operation:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"apple"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"banana"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"pear"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"kiwi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"orange"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("contains")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"a"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// prints: [apple, banana, pear, orange]")]),t._v("\n\n")])])]),s("p",[t._v("Other collection instances, such as a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Set.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Set")]),s("OutboundLink")],1),t._v(", can be made by using other "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Collectors")]),s("OutboundLink")],1),t._v(" built-in methods. For example, "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#toSet--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Collectors.toSet()")]),s("OutboundLink")],1),t._v(" collects the elements of a "),s("code",[t._v("Stream")]),t._v(" into a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Set.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Set")]),s("OutboundLink")],1),t._v(".")]),t._v(" "),s("h3",{attrs:{id:"explicit-control-over-the-implementation-of-list-or-set"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#explicit-control-over-the-implementation-of-list-or-set"}},[t._v("#")]),t._v(" Explicit control over the implementation of "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/List.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("List")]),s("OutboundLink")],1),t._v(" or "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Set.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Set")]),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("According to documentation of "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#toList--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Collectors#toList()")]),s("OutboundLink")],1),t._v(" and "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#toSet--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Collectors#toSet()")]),s("OutboundLink")],1),t._v(", there are no guarantees on the type, mutability, serializability, or thread-safety of the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/List.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("List")]),s("OutboundLink")],1),t._v(" or "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Set.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Set")]),s("OutboundLink")],1),t._v(" returned.")]),t._v(" "),s("p",[t._v("For explicit control over the implementation to be returned, "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#toCollection-java.util.function.Supplier-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Collectors#toCollection(Supplier)")]),s("OutboundLink")],1),t._v(" can be used instead, where the given supplier returns a new and empty collection.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// syntax with method reference")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("strings\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("null")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("&&")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("length")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toCollection")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("ArrayList")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// syntax with lambda")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("strings\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("null")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("&&")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("length")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toCollection")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedHashSet")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[s("strong",[t._v("Collecting Elements using "),s("a",{attrs:{href:"http://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#toMap-java.util.function.Function-java.util.function.Function-",target:"_blank",rel:"noopener noreferrer"}},[t._v("toMap"),s("OutboundLink")],1)])]),t._v(" "),s("p",[t._v("Collector accumulates elements into a Map, Where key is the Student Id and Value is Student Value.")]),t._v(" "),s("div",{staticClass:"language- extra-class"},[s("pre",{pre:!0,attrs:{class:"language-text"}},[s("code",[t._v('\n List<Student> students = new ArrayList<Student>(); \n    students.add(new Student(1,"test1"));\n    students.add(new Student(2,"test2"));\n    students.add(new Student(3,"test3"));\n    \n    Map<Integer, String> IdToName = students.stream()\n        .collect(Collectors.toMap(Student::getId, Student::getName));\n    System.out.println(IdToName);\n\n')])])]),s("p",[t._v("Output :")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v("test1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v("test2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v("test3"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("The Collectors.toMap has another implementation "),s("code",[t._v("Collector<T, ?, Map<K,U>> toMap(Function<? super T, ? extends K> keyMapper, Function<? super T, ? extends U> valueMapper, BinaryOperator<U> mergeFunction)")]),t._v(".The mergeFunction is mostly used to select either new value or retain old value if the key is repeated when adding a new member in the Map from a list.")]),t._v(" "),s("p",[t._v("The mergeFunction often looks like: "),s("code",[t._v("(s1, s2) -> s1")]),t._v(" to retain value corresponding to the repeated key, or "),s("code",[t._v("(s1, s2) -> s2")]),t._v(" to put new value for the repeated key.")]),t._v(" "),s("p",[s("strong",[t._v("Collecting Elements to Map of Collections")])]),t._v(" "),s("p",[t._v("Example: from ArrayList to Map<String, List<>>")]),t._v(" "),s("p",[t._v("Often it requires to make a map of list out of a primary list.\nExample: From a student of list, we need to make a map of list of subjects for each student.")]),t._v(" "),s("div",{staticClass:"language- extra-class"},[s("pre",{pre:!0,attrs:{class:"language-text"}},[s("code",[t._v('\n   List<Student> list = new ArrayList<>();\n    list.add(new Student("Davis", SUBJECT.MATH, 35.0));\n    list.add(new Student("Davis", SUBJECT.SCIENCE, 12.9));\n    list.add(new Student("Davis", SUBJECT.GEOGRAPHY, 37.0));\n\n    list.add(new Student("Sascha", SUBJECT.ENGLISH, 85.0));\n    list.add(new Student("Sascha", SUBJECT.MATH, 80.0));\n    list.add(new Student("Sascha", SUBJECT.SCIENCE, 12.0));\n    list.add(new Student("Sascha", SUBJECT.LITERATURE, 50.0));\n\n    list.add(new Student("Robert", SUBJECT.LITERATURE, 12.0));\n\n    Map<String, List<SUBJECT>> map = new HashMap<>();\n    list.stream().forEach(s -> {\n                map.computeIfAbsent(s.getName(), x -> new ArrayList<>()).add(s.getSubject());\n            });\n    System.out.println(map);\n\n')])])]),s("p",[t._v("Output:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Robert")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("LITERATURE"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Sascha")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("ENGLISH"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" MATH"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" SCIENCE"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" LITERATURE"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Davis")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("MATH"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" SCIENCE"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" GEOGRAPHY"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("Example: from ArrayList to Map<String, Map<>>")]),t._v(" "),s("div",{staticClass:"language- extra-class"},[s("pre",{pre:!0,attrs:{class:"language-text"}},[s("code",[t._v('\n   List<Student> list = new ArrayList<>();\n    list.add(new Student("Davis", SUBJECT.MATH, 1, 35.0));\n    list.add(new Student("Davis", SUBJECT.SCIENCE, 2, 12.9));\n    list.add(new Student("Davis", SUBJECT.MATH, 3, 37.0));\n    list.add(new Student("Davis", SUBJECT.SCIENCE, 4, 37.0));\n\n    list.add(new Student("Sascha", SUBJECT.ENGLISH, 5, 85.0));\n    list.add(new Student("Sascha", SUBJECT.MATH, 1, 80.0));\n    list.add(new Student("Sascha", SUBJECT.ENGLISH, 6, 12.0));\n    list.add(new Student("Sascha", SUBJECT.MATH, 3, 50.0));\n\n    list.add(new Student("Robert", SUBJECT.ENGLISH, 5, 12.0));\n\n    Map<String, Map<SUBJECT, List<Double>>> map = new HashMap<>();\n\n    list.stream().forEach(student -> {\n        map.computeIfAbsent(student.getName(), s -> new HashMap<>())\n                .computeIfAbsent(student.getSubject(), s -> new ArrayList<>())\n                .add(student.getMarks());\n    });\n\n    System.out.println(map);\n\n')])])]),s("p",[t._v("Output:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Robert")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("ENGLISH"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("12.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Sascha")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("MATH"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("80.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("50.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" ENGLISH"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("85.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("12.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Davis")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("MATH"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("35.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("37.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" SCIENCE"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("12.9")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("37.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("h3",{attrs:{id:"cheat-sheet"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#cheat-sheet"}},[t._v("#")]),t._v(" Cheat-Sheet")]),t._v(" "),s("table",[s("thead",[s("tr",[s("th",[t._v("Goal")]),t._v(" "),s("th",[t._v("Code")])])]),t._v(" "),s("tbody",[s("tr",[s("td",[t._v("Collect to a "),s("code",[t._v("List")])]),t._v(" "),s("td",[s("code",[t._v("Collectors.toList()")])])]),t._v(" "),s("tr",[s("td",[t._v("Collect to an "),s("code",[t._v("ArrayList")]),t._v(" with pre-allocated size")]),t._v(" "),s("td",[s("code",[t._v("Collectors.toCollection(() -> new ArrayList<>(size))")])])]),t._v(" "),s("tr",[s("td",[t._v("Collect to a "),s("code",[t._v("Set")])]),t._v(" "),s("td",[s("code",[t._v("Collectors.toSet()")])])]),t._v(" "),s("tr",[s("td",[t._v("Collect to a "),s("code",[t._v("Set")]),t._v(" with better iteration performance")]),t._v(" "),s("td",[s("code",[t._v("Collectors.toCollection(() -> new LinkedHashSet<>())")])])]),t._v(" "),s("tr",[s("td",[t._v("Collect to a case-insensitive "),s("code",[t._v("Set<String>")])]),t._v(" "),s("td",[s("code",[t._v("Collectors.toCollection(() -> new TreeSet<>(String.CASE_INSENSITIVE_ORDER))")])])]),t._v(" "),s("tr",[s("td",[t._v("Collect to an "),s("code",[t._v("EnumSet<AnEnum>")]),t._v(" (best performance for enums)")]),t._v(" "),s("td",[s("code",[t._v("Collectors.toCollection(() -> EnumSet.noneOf(AnEnum.class))")])])]),t._v(" "),s("tr",[s("td",[t._v("Collect to a "),s("code",[t._v("Map<K,V>")]),t._v(" with unique keys")]),t._v(" "),s("td",[s("code",[t._v("Collectors.toMap(keyFunc,valFunc)")])])]),t._v(" "),s("tr",[s("td",[t._v("Map MyObject.getter() to unique MyObject")]),t._v(" "),s("td",[s("code",[t._v("Collectors.toMap(MyObject::getter, Function.identity())")])])]),t._v(" "),s("tr",[s("td",[t._v("Map MyObject.getter() to multiple MyObjects")]),t._v(" "),s("td",[s("code",[t._v("Collectors.groupingBy(MyObject::getter)")])])])])]),t._v(" "),s("h2",{attrs:{id:"using-streams-to-implement-mathematical-functions"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#using-streams-to-implement-mathematical-functions"}},[t._v("#")]),t._v(" Using Streams to Implement Mathematical Functions")]),t._v(" "),s("p",[s("code",[t._v("Stream")]),t._v("s, and especially "),s("code",[t._v("IntStream")]),t._v("s, are an elegant way of implementing summation terms (∑). The ranges of the "),s("code",[t._v("Stream")]),t._v(" can be used as the bounds of the summation.")]),t._v(" "),s("p",[t._v("E.g., Madhava's approximation of Pi is given by the formula (Source: "),s("a",{attrs:{href:"https://en.wikipedia.org/wiki/Approximations_of_%CF%80",target:"_blank",rel:"noopener noreferrer"}},[t._v("wikipedia"),s("OutboundLink")],1),t._v("):\n"),s("a",{attrs:{href:"http://i.stack.imgur.com/XY9Kr.png",target:"_blank",rel:"noopener noreferrer"}},[s("img",{attrs:{src:"http://i.stack.imgur.com/XY9Kr.png",alt:"Madhava's approximation"}}),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("This can be calculated with an arbitrary precision. E.g., for 101 terms:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("double")]),t._v(" pi "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Math")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sqrt")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("12")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("*")]),t._v(" \n            "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("rangeClosed")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("100")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                     "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("mapToDouble")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("k "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Math")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("pow")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("-")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("-")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("*")]),t._v(" k"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("/")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("*")]),t._v(" k "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                     "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sum")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[s("strong",[t._v("Note:")]),t._v(" With "),s("code",[t._v("double")]),t._v("'s precision, selecting an upper bound of 29 is sufficient to get a result that's indistinguishable from "),s("code",[t._v("Math.Pi")]),t._v(".")]),t._v(" "),s("h2",{attrs:{id:"parallel-stream"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#parallel-stream"}},[t._v("#")]),t._v(" Parallel Stream")]),t._v(" "),s("p",[s("strong",[t._v("Note:")]),t._v(" Before deciding which "),s("code",[t._v("Stream")]),t._v(" to use please have a look at "),s("a",{attrs:{href:"http://stackoverflow.com/a/20375622/585398",target:"_blank",rel:"noopener noreferrer"}},[t._v("ParallelStream vs Sequential Stream behavior"),s("OutboundLink")],1),t._v(".")]),t._v(" "),s("p",[t._v("When you want to perform "),s("code",[t._v("Stream")]),t._v(" operations concurrently, you could use either of these ways.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" data "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"One"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Two"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Three"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Four"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Five"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" aParallelStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" data"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("parallel")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Or:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" aParallelStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" data"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("parallelStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("To execute the operations defined for the parallel stream, call a terminal operator:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[t._v("aParallelStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("(A possible) output from the parallel "),s("code",[t._v("Stream")]),t._v(":")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("Three"),s("br"),t._v("\nFour"),s("br"),t._v("\nOne"),s("br"),t._v("\nTwo"),s("br"),t._v("\nFive")]),t._v(" "),s("p",[t._v("The order might change as all the elements are processed in parallel (Which "),s("strong",[t._v("may")]),t._v(" make it faster). Use "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html#parallelStream--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("parallelStream")]),s("OutboundLink")],1),t._v(" when ordering does not matter.")]),t._v(" "),s("h3",{attrs:{id:"performance-impact"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#performance-impact"}},[t._v("#")]),t._v(" Performance impact")]),t._v(" "),s("p",[t._v("In case networking is involved, parallel "),s("code",[t._v("Stream")]),t._v("s may degrade the overall performance of an application because all parallel "),s("code",[t._v("Stream")]),t._v("s use a common fork-join thread pool for the network.")]),t._v(" "),s("p",[t._v("On the other hand, parallel "),s("code",[t._v("Stream")]),t._v("s may significantly improve performance in many other cases, depending of the number of available cores in the running CPU at the moment.")]),t._v(" "),s("h2",{attrs:{id:"flatten-streams-with-flatmap"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#flatten-streams-with-flatmap"}},[t._v("#")]),t._v(" Flatten Streams with flatMap()")]),t._v(" "),s("p",[t._v("A "),s("code",[t._v("Stream")]),t._v(" of items that are in turn streamable can be flattened into a single continuous "),s("code",[t._v("Stream")]),t._v(":")]),t._v(" "),s("p",[t._v("Array of List of Items can be converted into a single List.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list1 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v("  "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"one"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"two"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n      "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list2 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v("  "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"three"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"four"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"five"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n      "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list3 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v("  "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"six"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n          "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" finalList "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("list1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" list2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" list3"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("flatMap")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collection")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("finalList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// [one, two, three, four, five, six]")]),t._v("\n\n")])])]),s("p",[t._v("Map containing List of Items as values can be Flattened to a Combined List")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" map "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedHashMap")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nmap"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("put")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"a"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nmap"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("put")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"b"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("6")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" allValues "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" map"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("values")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Collection<List<Integer>>")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("                      "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Stream<List<Integer>>")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("flatMap")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("         "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Stream<Integer>")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("allValues"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// [1, 2, 3, 4, 5, 6]")]),t._v("\n\n")])])]),s("p",[s("code",[t._v("List")]),t._v(" of "),s("code",[t._v("Map")]),t._v(" can be flattened into a single continuous "),s("code",[t._v("Stream")])]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("ArrayList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" map1 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("HashMap")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nmap1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("put")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"1"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"one"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nmap1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("put")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"2"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"two"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" map2 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("HashMap")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nmap2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("put")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"3"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"three"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nmap2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("put")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"4"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"four"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nlist"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("map1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\nlist"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("map2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" output"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" list"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("  "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//  Stream<Map<String, String>>")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("values")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("              "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Stream<List<String>>")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("flatMap")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collection")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("   "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Stream<String>")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toSet")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("  "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//Set<String>")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// [one, two, three,four]")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"creating-a-stream"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#creating-a-stream"}},[t._v("#")]),t._v(" Creating a Stream")]),t._v(" "),s("p",[t._v("All java "),s("code",[t._v("Collection<E>")]),t._v("s have "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html#stream--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("stream()")]),s("OutboundLink")],1),t._v(" and "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Collection.html#parallelStream--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("parallelStream()")]),s("OutboundLink")],1),t._v(" methods from which a "),s("code",[t._v("Stream<E>")]),t._v(" can be constructed:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collection")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" stringList "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("ArrayList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" stringStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" stringList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("parallelStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("A "),s("code",[t._v("Stream<E>")]),t._v(" can be created from an array using one of two methods:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" values "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"aaa"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"bbbb"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"ddd"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"cccc"')]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" stringStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("values"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" stringStreamAlternative "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("values"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("The difference between "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Arrays.html#stream-T:A-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Arrays.stream()")]),s("OutboundLink")],1),t._v(" and "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#of-T...-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Stream.of()")]),s("OutboundLink")],1),t._v(" is that "),s("code",[t._v("Stream.of()")]),t._v(" has a varargs parameter, so it can be used like:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" integerStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("There are also primitive "),s("code",[t._v("Stream")]),t._v("s that you can use. For example:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),t._v(" intStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("DoubleStream")]),t._v(" doubleStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("DoubleStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3.0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("These primitive streams can also be constructed using the "),s("code",[t._v("Arrays.stream()")]),t._v(" method:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),t._v(" intStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("int")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("It is possible to create a "),s("code",[t._v("Stream")]),t._v(" from an array with a specified range.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("int")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" values"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("int")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),t._v(" intStram "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("values"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Note that any primitive stream can be converted to boxed type stream using the "),s("code",[t._v("boxed")]),t._v(" method :")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" integerStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" intStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("boxed")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("This can be useful in some case if you want to collect the data since primitive stream does not have any "),s("code",[t._v("collect")]),t._v(" method that takes a "),s("code",[t._v("Collector")]),t._v(" as argument.")]),t._v(" "),s("p",[s("strong",[t._v("Reusing intermediate operations of a stream chain")])]),t._v(" "),s("p",[t._v("Stream is closed when ever terminal operation is called. Reusing the stream of intermediate operations, when only terminal operation is only varying.\nwe could create a stream supplier to construct a new stream with all intermediate operations already set up.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Supplier")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" streamSupplier "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"apple"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"banana"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"orange"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"grapes"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"melon"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"blueberry"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"blackberry"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toUpperCase")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n  streamSupplier"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("get")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v("   s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("startsWith")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"A"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// APPLE")]),t._v("\n\n  streamSupplier"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("get")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("startsWith")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"B"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n  "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// BANANA")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// BLACKBERRY")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// BLUEBERRY")]),t._v("\n\n")])])]),s("p",[s("code",[t._v("int[]")]),t._v(" arrays can be converted to "),s("code",[t._v("List<Integer>")]),t._v(" using streams")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("int")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" ints "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("ints"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("boxed")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"finding-statistics-about-numerical-streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#finding-statistics-about-numerical-streams"}},[t._v("#")]),t._v(" Finding Statistics about Numerical Streams")]),t._v(" "),s("p",[t._v("Java 8 provides classes called "),s("a",{attrs:{href:"http://docs.oracle.com/javase/8/docs/api/java/util/IntSummaryStatistics.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("IntSummaryStatistics")]),s("OutboundLink")],1),t._v(", "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/DoubleSummaryStatistics.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("DoubleSummaryStatistics")]),s("OutboundLink")],1),t._v("  and "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/LongSummaryStatistics.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("LongSummaryStatistics")]),s("OutboundLink")],1),t._v(" which give a state object for collecting statistics such as "),s("code",[t._v("count")]),t._v(", "),s("code",[t._v("min")]),t._v(", "),s("code",[t._v("max")]),t._v(", "),s("code",[t._v("sum")]),t._v(", and "),s("code",[t._v("average")]),t._v(".")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" naturalNumbers "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("4")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("6")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("7")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("8")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("9")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntSummaryStatistics")]),t._v(" stats "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" naturalNumbers"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                                           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("mapToInt")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("x"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" x"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n                                           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("summaryStatistics")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("stats"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Which will result in:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntSummaryStatistics")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("count"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" sum"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("55")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" min"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" max"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" average"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("5.500000")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"using-intstream-to-iterate-over-indexes"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#using-intstream-to-iterate-over-indexes"}},[t._v("#")]),t._v(" Using IntStream to iterate over indexes")]),t._v(" "),s("p",[s("code",[t._v("Stream")]),t._v("s of elements usually do not allow access to the index value of the current item. To iterate over an array or "),s("code",[t._v("ArrayList")]),t._v(" while having access to indexes, use "),s("code",[t._v("IntStream.range(start, endExclusive)")]),t._v(".")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" names "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Jon"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Darin"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Bauke"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Hans"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Marc"')]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("range")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" names"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("length"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("mapToObj")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("format")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"#%d %s"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" names"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("i"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("The "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/IntStream.html#range-int-int-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("range(start, endExclusive)")]),s("OutboundLink")],1),t._v(" method returns another "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/IntStream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("ÌntStream")]),s("OutboundLink")],1),t._v(" and the "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/IntStream.html#mapToObj-java.util.function.IntFunction-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("mapToObj(mapper)")]),s("OutboundLink")],1),t._v(" returns a stream of "),s("code",[t._v("String")]),t._v(".")]),t._v(" "),s("p",[t._v("Output:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("#1 Jon"),s("br"),t._v("\n#2 Darin"),s("br"),t._v("\n#3 Bauke"),s("br"),t._v("\n#4 Hans"),s("br"),t._v("\n#5 Marc")]),t._v(" "),s("p",[t._v("This is very similar to using a normal "),s("code",[t._v("for")]),t._v(" loop with a counter, but with the benefit of pipelining and parallelization:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("for")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("int")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<")]),t._v(" names"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("length"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" i"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("++")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" newName "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("format")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"#%d %s"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" names"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),t._v("i"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("newName"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"converting-an-iterator-to-a-stream"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#converting-an-iterator-to-a-stream"}},[t._v("#")]),t._v(" Converting an iterator to a stream")]),t._v(" "),s("p",[t._v("Use "),s("code",[t._v("Spliterators.spliterator()")]),t._v(" or "),s("code",[t._v("Spliterators.spliteratorUnknownSize()")]),t._v(" to convert an iterator to a stream:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Iterator")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" iterator "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"A"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"B"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"C"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("iterator")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("    \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Spliterator")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" spliterator "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Spliterators")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("spliteratorUnknownSize")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("iterator"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" stream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("StreamSupport")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("spliterator"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token boolean"}},[t._v("false")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"concatenate-streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#concatenate-streams"}},[t._v("#")]),t._v(" Concatenate Streams")]),t._v(" "),s("p",[t._v("Variable declaration for examples:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collection")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" abc "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"a"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"b"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"c"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collection")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" digits "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"1"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"2"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"3"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collection")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" greekAbc "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"alpha"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"beta"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"gamma"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[s("strong",[t._v("Example 1 - Concatenate two "),s("code",[t._v("Stream")]),t._v("s")])]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("final")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" concat1 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("concat")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("abc"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" digits"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\nconcat1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("print")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// prints: abc123")]),t._v("\n\n")])])]),s("p",[s("strong",[t._v("Example 2 - Concatenate more than two "),s("code",[t._v("Stream")]),t._v("s")])]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("final")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" concat2 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("concat")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("concat")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("abc"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" digits"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    greekAbc"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("concat2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("joining")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('", "')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// prints: a, b, c, 1, 2, 3, alpha, beta, gamma")]),t._v("\n\n")])])]),s("p",[t._v("Alternatively to simplify the nested "),s("code",[t._v("concat()")]),t._v(" syntax the "),s("code",[t._v("Stream")]),t._v("s can also be concatenated with "),s("code",[t._v("flatMap()")]),t._v(":")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("final")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" concat3 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("\n    abc"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" digits"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" greekAbc"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("flatMap")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// or `.flatMap(Function.identity());` (java.util.function.Function)")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("concat3"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("joining")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('", "')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// prints: a, b, c, 1, 2, 3, alpha, beta, gamma")]),t._v("\n\n")])])]),s("p",[t._v("Be careful when constructing "),s("code",[t._v("Stream")]),t._v("s from repeated concatenation, because accessing an element of a deeply concatenated "),s("code",[t._v("Stream")]),t._v(" can result in deep call chains or even a "),s("code",[t._v("StackOverflowException")]),t._v(".")]),t._v(" "),s("h2",{attrs:{id:"intstream-to-string"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#intstream-to-string"}},[t._v("#")]),t._v(" IntStream to String")]),t._v(" "),s("p",[t._v("Java does not have a "),s("strong",[t._v("Char Stream")]),t._v(", so when working with "),s("code",[t._v("String")]),t._v("s and constructing a "),s("code",[t._v("Stream")]),t._v(" of "),s("code",[t._v("Character")]),t._v("s, an option is to get a "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/IntStream.html",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("IntStream")]),s("OutboundLink")],1),t._v(" of code points using "),s("code",[t._v("String.codePoints()")]),t._v(" method. So "),s("code",[t._v("IntStream")]),t._v(" can be obtained as below:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stringToIntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" in"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" in"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("codePoints")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("It is a bit more involved to do the conversion other way around i.e. IntStreamToString. That can be done as follows:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("intStreamToString")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),t._v(" intStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n  "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" intStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("StringBuilder")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("StringBuilder")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("appendCodePoint")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("StringBuilder")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("append")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toString")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"finding-the-first-element-that-matches-a-predicate"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#finding-the-first-element-that-matches-a-predicate"}},[t._v("#")]),t._v(" Finding the First Element that Matches a Predicate")]),t._v(" "),s("p",[t._v("It is possible to find the first element of a "),s("code",[t._v("Stream")]),t._v(" that matches a condition.")]),t._v(" "),s("p",[t._v("For this example, we will find the first "),s("code",[t._v("Integer")]),t._v(" whose square is over "),s("code",[t._v("50000")]),t._v(".")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("iterate")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Generate an infinite stream 1,2,3,4...")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("i"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("*")]),t._v("i"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v(">")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("50000")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Filter to find elements where the square is >50000")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("findFirst")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Find the first filtered element")]),t._v("\n\n")])])]),s("p",[t._v("This expression will return an "),s("code",[t._v("OptionalInt")]),t._v(" with the result.")]),t._v(" "),s("p",[t._v("Note that with an infinite "),s("code",[t._v("Stream")]),t._v(", Java will keep checking each element until it finds a result. With a finite "),s("code",[t._v("Stream")]),t._v(", if Java runs out of elements but still can't find a result, it returns an empty "),s("code",[t._v("OptionalInt")]),t._v(".")]),t._v(" "),s("h2",{attrs:{id:"using-streams-and-method-references-to-write-self-documenting-processes"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#using-streams-and-method-references-to-write-self-documenting-processes"}},[t._v("#")]),t._v(" Using Streams and Method References to Write Self-Documenting Processes")]),t._v(" "),s("p",[t._v("Method references make excellent self-documenting code, and using method references with "),s("code",[t._v("Stream")]),t._v("s makes complicated processes simple to read and understand. Consider the following code:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("interface")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Ordered")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("default")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("int")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getOrder")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("interface")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Valued")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("extends")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Ordered")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("boolean")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hasPropertyTwo")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getValue")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("interface")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Thing")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("extends")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Ordered")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("boolean")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hasPropertyOne")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Valued")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getValuedProperty")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("extends")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Ordered")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("myMethod")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Thing")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" things"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" results "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("ArrayList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("for")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Thing")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" thing "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v(":")]),t._v(" things"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("thing"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hasPropertyOne")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n            "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Valued")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" valued "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" thing"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getValuedProperty")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n            "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("valued "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("null")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("&&")]),t._v(" valued"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hasPropertyTwo")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n                "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),t._v(" value "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" valued"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getValue")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n                "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("if")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("value "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("!=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("null")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n                    results"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("value"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n                "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n            "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n    results"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sort")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("a"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" b"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("compare")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("a"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getOrder")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" b"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getOrder")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" results"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("This last method rewritten using "),s("code",[t._v("Stream")]),t._v("s and method references is much more legible and each step of the process is quickly and easily understood - it's not just shorter, it also shows at a glance which interfaces and classes are responsible for the code in each step:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("extends")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Ordered")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("myMethod")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Thing")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" things"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" things"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Thing")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hasPropertyOne")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Thing")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getValuedProperty")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Objects")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("nonNull")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Valued")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hasPropertyTwo")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Valued")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getValue")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Objects")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("nonNull")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Comparator")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("comparing")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Ordered")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getOrder")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("    \n\n")])])]),s("h2",{attrs:{id:"using-streams-of-map-entry-to-preserve-initial-values-after-mapping"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#using-streams-of-map-entry-to-preserve-initial-values-after-mapping"}},[t._v("#")]),t._v(" Using Streams of Map.Entry to Preserve Initial Values after Mapping")]),t._v(" "),s("p",[t._v("When you have a "),s("code",[t._v("Stream")]),t._v(" you need to map but want to preserve the initial values as well, you can map the "),s("code",[t._v("Stream")]),t._v(" to a "),s("code",[t._v("Map.Entry<K,V>")]),t._v(" using a utility method like the following:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("static")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("K")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Function")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("K")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("Entry")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("K")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("entryMapper")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Function")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("K")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" mapper"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("k"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("AbstractMap"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("SimpleEntry")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("k"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" mapper"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("apply")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("k"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("Then you can use your converter to process "),s("code",[t._v("Stream")]),t._v("s having access to both the original and mapped values:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Set")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("K")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" mySet"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Function")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("K")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" transformer "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("SomeClass")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("transformerMethod")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("Entry")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("K")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("V")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" entryStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" mySet"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("entryMapper")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("transformer"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("You can then continue to process that "),s("code",[t._v("Stream")]),t._v(" as normal. This avoids the overhead of creating an intermediate collection.")]),t._v(" "),s("h2",{attrs:{id:"reduction-with-streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#reduction-with-streams"}},[t._v("#")]),t._v(" Reduction with Streams")]),t._v(" "),s("p",[t._v("Reduction is the process of applying a binary operator to every element of a stream to result in one value.")]),t._v(" "),s("p",[t._v("The "),s("code",[t._v("sum()")]),t._v(" method of an "),s("code",[t._v("IntStream")]),t._v(" is an example of a reduction; it applies addition to every term of the Stream, resulting in one final value:\n"),s("a",{attrs:{href:"http://i.stack.imgur.com/2Krwx.png",target:"_blank",rel:"noopener noreferrer"}},[s("img",{attrs:{src:"http://i.stack.imgur.com/2Krwx.png",alt:"Sum Reduction"}}),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("This is equivalent to "),s("code",[t._v("(((1+2)+3)+4)")])]),t._v(" "),s("p",[t._v("The "),s("code",[t._v("reduce")]),t._v(" method of a Stream allows one to create a custom reduction. It is possible to use the "),s("code",[t._v("reduce")]),t._v(" method to implement the "),s("code",[t._v("sum()")]),t._v(" method:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),t._v(" istr"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    \n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//Initialize istr")]),t._v("\n    \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("OptionalInt")]),t._v(" istr"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("reduce")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("a"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("b"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v("a"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v("b"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("The "),s("code",[t._v("Optional")]),t._v(" version is returned so that empty Streams can be handled appropriately.")]),t._v(" "),s("p",[t._v("Another example of reduction is combining a "),s("code",[t._v("Stream<LinkedList<T>>")]),t._v(" into a single "),s("code",[t._v("LinkedList<T>")]),t._v(":")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" listStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    \n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//Create a Stream<LinkedList<T>>")]),t._v("\n    \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Optional")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" bigList "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" listStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("reduce")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" retList "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    retList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addAll")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("list1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    retList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addAll")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("list2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" retList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("You can also provide an "),s("strong",[t._v("identity element")]),t._v(". For example, the identity element for addition is 0, as "),s("code",[t._v("x+0==x")]),t._v(". For multiplication, the identity element is 1, as "),s("code",[t._v("x*1==x")]),t._v(". In the case above, the identity element is an empty "),s("code",[t._v("LinkedList<T>")]),t._v(', because if you add an empty list to another list, the list that you are "adding" to doesn\'t change:')]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" listStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//Create a Stream<LinkedList<T>>")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" bigList "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" listStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("reduce")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" list2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" retList "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("LinkedList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    retList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addAll")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("list1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    retList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("addAll")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("list2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" retList"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Note that when an identity element is provided, the return value is not wrapped in an "),s("code",[t._v("Optional")]),t._v("—if called on an empty stream, "),s("code",[t._v("reduce()")]),t._v(" will return the identity element.")]),t._v(" "),s("p",[t._v("The binary operator must also be "),s("strong",[t._v("associative")]),t._v(", meaning that "),s("code",[t._v("(a+b)+c==a+(b+c)")]),t._v(". This is because the elements may be reduced in any order. For example, the above addition reduction could be performed like this:")]),t._v(" "),s("p",[s("a",{attrs:{href:"http://i.stack.imgur.com/sCqVF.png",target:"_blank",rel:"noopener noreferrer"}},[s("img",{attrs:{src:"http://i.stack.imgur.com/sCqVF.png",alt:"Other sum reduction"}}),s("OutboundLink")],1)]),t._v(" "),s("p",[t._v("This reduction is equivalent to writing "),s("code",[t._v("((1+2)+(3+4))")]),t._v(". The property of associativity also allows Java to reduce the "),s("code",[t._v("Stream")]),t._v(" in parallel—a portion of the Stream can be reduced by each processor, with a reduction combining the result of each processor at the end.")]),t._v(" "),s("h2",{attrs:{id:"converting-a-stream-of-optional-to-a-stream-of-values"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#converting-a-stream-of-optional-to-a-stream-of-values"}},[t._v("#")]),t._v(" Converting a Stream of Optional to a Stream of Values")]),t._v(" "),s("p",[t._v("You may need to convert a "),s("code",[t._v("Stream")]),t._v(" emitting "),s("code",[t._v("Optional")]),t._v(" to a "),s("code",[t._v("Stream")]),t._v(" of values, emitting only values from existing "),s("code",[t._v("Optional")]),t._v(". (ie: without "),s("code",[t._v("null")]),t._v(" value and not dealing with "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/Optional.html#empty--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Optional.empty()")]),s("OutboundLink")],1),t._v(").")]),t._v(" "),s("div",{staticClass:"language- extra-class"},[s("pre",{pre:!0,attrs:{class:"language-text"}},[s("code",[t._v('\nOptional<String> op1 = Optional.empty();\n Optional<String> op2 = Optional.of("Hello World");\n\n List<String> result = Stream.of(op1, op2)\n                             .filter(Optional::isPresent)\n                             .map(Optional::get)\n                             .collect(Collectors.toList());\n\n System.out.println(result); //[Hello World]\n\n')])])]),s("h2",{attrs:{id:"get-a-slice-of-a-stream"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#get-a-slice-of-a-stream"}},[t._v("#")]),t._v(" Get a Slice of a Stream")]),t._v(" "),s("p",[s("strong",[t._v("Example:")]),t._v(" Get a "),s("code",[t._v("Stream")]),t._v(" of 30 elements, containing 21st to 50th (inclusive) element of a collection.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("final")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("long")]),t._v(" n "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("20L")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// the number of elements to skip")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("final")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("long")]),t._v(" maxSize "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("30L")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// the number of elements the stream should be limited to")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("final")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("T")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" slice "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" collection"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("skip")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("limit")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("maxSize"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[s("strong",[t._v("Notes:")])]),t._v(" "),s("li",[t._v("`IllegalArgumentException` is thrown if `n` is negative or `maxSize`\nis negative")]),t._v("\n- both `skip(long)` and `limit(long)` are intermediate operations\n- if a stream contains fewer than `n` elements then `skip(n)` returns an empty stream\n- both `skip(long)` and `limit(long)` are cheap operations on sequential stream pipelines, but can be quite expensive on ordered parallel pipelines\n"),s("h2",{attrs:{id:"create-a-map-based-on-a-stream"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#create-a-map-based-on-a-stream"}},[t._v("#")]),t._v(" Create a Map based on a Stream")]),t._v(" "),s("p",[s("strong",[t._v("Simple case without duplicate keys")])]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" characters "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"A"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"B"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"C"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" map "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" characters\n            "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toMap")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("element "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" element"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hashCode")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" element "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" element"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// map = {65=A, 66=B, 67=C}")]),t._v("\n\n")])])]),s("p",[t._v("To make things more declarative, we can use static method in "),s("code",[t._v("Function")]),t._v(" interface - "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/function/Function.html#identity--",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Function.identity()")]),s("OutboundLink")],1),t._v(". We can replace this lambda "),s("code",[t._v("element -> element")]),t._v(" with "),s("code",[t._v("Function.identity()")]),t._v(".")]),t._v(" "),s("p",[s("strong",[t._v("Case where there might be duplicate keys")])]),t._v(" "),s("p",[t._v("The "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#toMap-java.util.function.Function-java.util.function.Function-java.util.function.BinaryOperator-",target:"_blank",rel:"noopener noreferrer"}},[t._v("javadoc"),s("OutboundLink")],1),t._v(" for "),s("code",[t._v("Collectors.toMap")]),t._v(" states:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("If the mapped keys contains duplicates (according to "),s("code",[t._v("Object.equals(Object)")]),t._v("), an "),s("code",[t._v("IllegalStateException")]),t._v(" is thrown when the collection operation is performed. If the mapped keys may have duplicates, use "),s("code",[t._v("toMap(Function, Function, BinaryOperator)")]),t._v(" instead.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" characters "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"A"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"B"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"B"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"C"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Integer")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" map "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" characters\n            "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toMap")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("\n                element "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" element"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("hashCode")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n                element "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" element"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n                "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("existingVal"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" newVal"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("existingVal "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" newVal"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// map = {65=A, 66=BB, 67=C}")]),t._v("\n\n")])])]),s("p",[t._v("The "),s("code",[t._v("BinaryOperator")]),t._v(" passed to "),s("code",[t._v("Collectors.toMap(...)")]),t._v(" generates the value to be stored in the case of a collision.  It can:")]),t._v(" "),s("ul",[s("li",[t._v("return the old value, so that the first value in the stream takes precedence,")]),t._v(" "),s("li",[t._v("return the new value, so that the last value in the stream takes precedence, or")]),t._v(" "),s("li",[t._v("combine the old and new values")])]),t._v(" "),s("p",[s("strong",[t._v("Grouping by value")])]),t._v(" "),s("p",[t._v("You can use "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Collectors.html#groupingBy-java.util.function.Function-java.util.stream.Collector-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("Collectors.groupingBy")]),s("OutboundLink")],1),t._v(' when you need to perform the equivalent of a database cascaded "group by" operation.  To illustrate, the following creates a map in which people\'s names are mapped to surnames:')]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Person")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" people "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Person")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Sam"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Rossi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Person")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Sam"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Verdi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Person")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"John"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Bianchi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Person")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"John"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Rossi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Person")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"John"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Verdi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Map")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" map "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" people"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("\n                "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// function mapping input elements to keys")]),t._v("\n                "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("groupingBy")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Person")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getName")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" \n                "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// function mapping input elements to values,")]),t._v("\n                "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// how to store values")]),t._v("\n                "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("mapping")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Person")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getSurname")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n        "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// map = {John=[Bianchi, Rossi, Verdi], Sam=[Rossi, Verdi]}")]),t._v("\n\n")])])]),s("p",[s("a",{attrs:{href:"https://ideone.com/2Ar9IA",target:"_blank",rel:"noopener noreferrer"}},[t._v("Live on Ideone"),s("OutboundLink")],1)]),t._v(" "),s("h2",{attrs:{id:"sort-using-stream"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#sort-using-stream"}},[t._v("#")]),t._v(" Sort Using Stream")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" data "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("ArrayList")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\ndata"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Sydney"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\ndata"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"London"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\ndata"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"New York"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\ndata"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Amsterdam"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\ndata"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Mumbai"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\ndata"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("add")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"California"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("data"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" sortedData "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" data"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("sortedData"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Output:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Sydney")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("London")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("New")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("York")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Amsterdam")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Mumbai")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("California")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Amsterdam")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("California")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("London")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Mumbai")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("New")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("York")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Sydney")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v("\n\n")])])]),s("p",[t._v("It's also possible to use different comparison mechanism as there is a overloaded "),s("a",{attrs:{href:"https://docs.oracle.com/javase/8/docs/api/java/util/stream/Stream.html#sorted-java.util.Comparator-",target:"_blank",rel:"noopener noreferrer"}},[s("code",[t._v("sorted")]),s("OutboundLink")],1),t._v(" version which takes a comparator as its argument.")]),t._v(" "),s("p",[t._v("Also, you can use a lambda expression for sorting:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" sortedData2 "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" data"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v("s2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s2"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("compareTo")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s1"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("This would output "),s("code",[t._v("[Sydney, New York, Mumbai, London, California, Amsterdam]")])]),t._v(" "),s("p",[t._v("You can use "),s("code",[t._v("Comparator.reverseOrder()")]),t._v(" to have a comparator that imposes the "),s("code",[t._v("reverse")]),t._v(" of the natural ordering.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" reverseSortedData "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" data"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Comparator")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("reverseOrder")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"streams-of-primitives"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#streams-of-primitives"}},[t._v("#")]),t._v(" Streams of Primitives")]),t._v(" "),s("p",[t._v("Java provides specialized "),s("code",[t._v("Stream")]),t._v("s for three types of primitives "),s("code",[t._v("IntStream")]),t._v(" (for "),s("code",[t._v("int")]),t._v("s), "),s("code",[t._v("LongStream")]),t._v(" (for "),s("code",[t._v("long")]),t._v("s) and "),s("code",[t._v("DoubleStream")]),t._v(" (for "),s("code",[t._v("double")]),t._v("s). Besides being optimized implementations for their respective primitives, they also provide several specific terminal methods, typically for mathematical operations. E.g.:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),t._v(" is "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("10")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("20")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("30")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("double")]),t._v(" average "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" is"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("average")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("getAsDouble")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// average is 20.0")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"stream-operations-categories"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#stream-operations-categories"}},[t._v("#")]),t._v(" Stream operations categories")]),t._v(" "),s("p",[t._v("Stream operations fall into two main categories, intermediate and terminal operations, and two sub-categories, stateless and stateful.")]),t._v(" "),s("h3",{attrs:{id:"intermediate-operations"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#intermediate-operations"}},[t._v("#")]),t._v(" Intermediate Operations:")]),t._v(" "),s("p",[t._v("An intermediate operation is always "),s("strong",[t._v("lazy")]),t._v(", such as a simple "),s("code",[t._v("Stream.map")]),t._v(". It is not invoked until the stream is actually consumed. This can be verified easily:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("2")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("3")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("throw")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("RuntimeException")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"not gonna happen"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" i"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Intermediate operations are the common building blocks of a stream, chained after the source and are usually followed by a terminal operation triggering the stream chain.")]),t._v(" "),s("h3",{attrs:{id:"terminal-operations"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#terminal-operations"}},[t._v("#")]),t._v(" Terminal Operations")]),t._v(" "),s("p",[t._v("Terminal operations are what triggers the consumption of a stream. Some of the more common are "),s("code",[t._v("Stream.forEach")]),t._v(" or "),s("code",[t._v("Stream.collect")]),t._v(". They are usually placed after a chain of intermediate operations and are almost always "),s("strong",[t._v("eager")]),t._v(".")]),t._v(" "),s("h3",{attrs:{id:"stateless-operations"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#stateless-operations"}},[t._v("#")]),t._v(" Stateless Operations")]),t._v(" "),s("p",[t._v("Statelessness means that each item is processed without the context of other items. Stateless operations allow for memory-efficient processing of streams.  Operations like "),s("code",[t._v("Stream.map")]),t._v(" and "),s("code",[t._v("Stream.filter")]),t._v(" that do not require information on other items of the stream are considered to be stateless.")]),t._v(" "),s("h3",{attrs:{id:"stateful-operations"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#stateful-operations"}},[t._v("#")]),t._v(" Stateful operations")]),t._v(" "),s("p",[t._v("Statefulness means the operation on each item depends on (some) other items of the stream. This requires a state to be preserved. Statefulness operations may break with long, or infinite, streams.  Operations like "),s("code",[t._v("Stream.sorted")]),t._v(" require the entirety of the stream to be processed before any item is emitted which will break in a long enough stream of items. This can be demonstrated by a long stream ("),s("strong",[t._v("run at your own risk")]),t._v("):")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// works - stateless stream")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("long")]),t._v(" BIG_ENOUGH_NUMBER "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("999999999")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("iterate")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("limit")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("BIG_ENOUGH_NUMBER"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("This will cause an out-of-memory due to statefulness of "),s("code",[t._v("Stream.sorted")]),t._v(":")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// Out of memory - stateful stream")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("IntStream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("iterate")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("0")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("+")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("1")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("limit")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("BIG_ENOUGH_NUMBER"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("forEach")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("h2",{attrs:{id:"joining-a-stream-to-a-single-string"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#joining-a-stream-to-a-single-string"}},[t._v("#")]),t._v(" Joining a stream to a single String")]),t._v(" "),s("p",[t._v("A use case that comes across frequently, is creating a "),s("code",[t._v("String")]),t._v(" from a stream, where the stream-items are separated by a certain character. The "),s("code",[t._v("Collectors.joining()")]),t._v(" method can be used for this, like in the following example:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" fruitStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("of")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"apple"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"banana"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"pear"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"kiwi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"orange"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" result "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" fruitStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("contains")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"a"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toUpperCase")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("joining")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('", "')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n           \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("result"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Output:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("APPLE, BANANA, ORANGE, PEAR")]),t._v(" "),s("p",[t._v("The "),s("code",[t._v("Collectors.joining()")]),t._v(" method can also cater for pre- and postfixes:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" result "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" fruitStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("contains")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"e"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("map")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toUpperCase")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("sorted")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n           "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Collectors")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("joining")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('", "')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"Fruits: "')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"."')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n           \n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("result"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[t._v("Output:")]),t._v(" "),s("blockquote"),t._v(" "),s("p",[t._v("Fruits: APPLE, ORANGE, PEAR.")]),t._v(" "),s("p",[s("a",{attrs:{href:"http://ideone.com/e.js/MH4kmG",target:"_blank",rel:"noopener noreferrer"}},[t._v("Live on Ideone"),s("OutboundLink")],1)]),t._v(" "),s("h2",{attrs:{id:"collect-results-of-a-stream-into-an-array"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#collect-results-of-a-stream-into-an-array"}},[t._v("#")]),t._v(" Collect Results of a Stream into an Array")]),t._v(" "),s("p",[t._v("Analog to get a collection for a "),s("code",[t._v("Stream")]),t._v(" by "),s("code",[t._v("collect()")]),t._v(" an array can be obtained by the "),s("code",[t._v("Stream.toArray()")]),t._v(" method:")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("List")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" fruits "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("asList")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"apple"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"banana"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"pear"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"kiwi"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"orange"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),t._v(" filteredFruits "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" fruits"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("stream")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("s "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" s"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("contains")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token string"}},[t._v('"a"')]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toArray")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("[")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("]")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("     \n\n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("// prints: [apple, banana, pear, orange]")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("System")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("out"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("println")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Arrays")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toString")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("filteredFruits"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n")])])]),s("p",[s("code",[t._v("String[]::new")]),t._v(" is a special kind of method reference: a constructor reference.")]),t._v(" "),s("h2",{attrs:{id:"generating-random-strings-using-streams"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#generating-random-strings-using-streams"}},[t._v("#")]),t._v(" Generating random Strings using Streams")]),t._v(" "),s("p",[t._v("It is sometimes useful to create random "),s("code",[t._v("Strings")]),t._v(", maybe as Session-ID for a web-service or an initial password after registration for an application.\nThis can be easily achieved using "),s("code",[t._v("Stream")]),t._v("s.")]),t._v(" "),s("p",[t._v("First we need to initialize a random number generator. To enhance security for the generated "),s("code",[t._v("String")]),t._v("s, it is a good idea to use "),s("code",[t._v("SecureRandom")]),t._v(".")]),t._v(" "),s("p",[s("strong",[t._v("Note")]),t._v(": Creating a "),s("code",[t._v("SecureRandom")]),t._v(" is quite expensive, so it is best practice to only do this once and call one of its "),s("code",[t._v("setSeed()")]),t._v(" methods from time to time to reseed it.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("private")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("static")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("final")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("SecureRandom")]),t._v(" rng "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("SecureRandom")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("SecureRandom")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("generateSeed")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token number"}},[t._v("20")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v(" \n"),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//20 Bytes as a seed is rather arbitrary, it is the number used in the JavaDoc example")]),t._v("\n\n")])])]),s("p",[t._v("When creating random "),s("code",[t._v("String")]),t._v("s, we usually want them to use only certain characters (e.g. only letters and digits). Therefore we can create a method returning a "),s("code",[t._v("boolean")]),t._v(" which can later be used to filter the "),s("code",[t._v("Stream")]),t._v(".")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//returns true for all chars in 0-9, a-z and A-Z")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("boolean")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("useThisCharacter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("char")]),t._v(" c"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//check for range to avoid using all unicode Letter (e.g. some chinese symbols)")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" c "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v(">=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'0'")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("&&")]),t._v(" c "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("<=")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token string"}},[t._v("'z'")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("&&")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Character")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("isLetterOrDigit")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("c"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("p",[t._v("Next we can utilize the RNG to generate a random String of specific length containing the charset which pass our "),s("code",[t._v("useThisCharacter")]),t._v(" check.")]),t._v(" "),s("div",{staticClass:"language-java extra-class"},[s("pre",{pre:!0,attrs:{class:"language-java"}},[s("code",[s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("public")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("generateRandomString")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("long")]),t._v(" length"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("{")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//Since there is no native CharStream, we use an IntStream instead")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//and convert it to a Stream<Character> using mapToObj.")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//We need to specify the boundaries for the int values to ensure they can safely be cast to char")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Stream")]),s("span",{pre:!0,attrs:{class:"token generics"}},[s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("<")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Character")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(">")])]),t._v(" randomCharStream "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" rng"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("ints")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Character")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("MIN_CODE_POINT"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("Character")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),t._v("MAX_CODE_POINT"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("mapToObj")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("i "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("char")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),t._v("i"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("filter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("c "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("->")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("this")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("useThisCharacter")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("limit")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),t._v("length"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n\n    "),s("span",{pre:!0,attrs:{class:"token comment"}},[t._v("//now we can use this Stream to build a String utilizing the collect method.")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("String")]),t._v(" randomString "),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("=")]),t._v(" randomCharStream"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("collect")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("StringBuilder")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("new")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("StringBuilder")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("append")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(",")]),t._v(" "),s("span",{pre:!0,attrs:{class:"token class-name"}},[t._v("StringBuilder")]),s("span",{pre:!0,attrs:{class:"token operator"}},[t._v("::")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("append")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(".")]),s("span",{pre:!0,attrs:{class:"token function"}},[t._v("toString")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("(")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(")")]),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n    "),s("span",{pre:!0,attrs:{class:"token keyword"}},[t._v("return")]),t._v(" randomString"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v(";")]),t._v("\n"),s("span",{pre:!0,attrs:{class:"token punctuation"}},[t._v("}")]),t._v("\n\n")])])]),s("h4",{attrs:{id:"syntax"}},[s("a",{staticClass:"header-anchor",attrs:{href:"#syntax"}},[t._v("#")]),t._v(" Syntax")]),t._v(" "),s("ul",[s("li",[t._v("collection.stream()")]),t._v(" "),s("li",[t._v("Arrays.stream(array)")]),t._v(" "),s("li",[t._v("Stream.iterate(firstValue, currentValue -> nextValue)")]),t._v(" "),s("li",[t._v("Stream.generate(() -> value)")]),t._v(" "),s("li",[t._v("Stream.of(elementOfT[, elementOfT, ...])")]),t._v(" "),s("li",[t._v("Stream.empty()")]),t._v(" "),s("li",[t._v("StreamSupport.stream( iterable.spliterator(), false )")])])])}),[],!1,null,null,null);a.default=e.exports}}]);