Java 8 In Action exercise！

Qiu1024 · Qiu1024 · commit 99e43b7b5fe0 · 2019-07-02T21:51:57.000+08:00
diff --git a/src/main/java/com/rice/java8/samples/lambda/Java8InActionTest.java b/src/main/java/com/rice/java8/samples/lambda/Java8InActionTest.java
@@ -0,0 +1,95 @@
+package com.rice.java8.samples.lambda;
+
+import com.rice.java8.samples.test.AbstractBaseTest;
+import org.junit.Test;
+
+/**
+ * 测验3.4:函数式接口 对于下列函数描述符(即Lambda表达式的签名)，你会使用哪些函数式接口?在表3-2中
+ * 可以找到大部分答案。作为进一步练习，请构造一个可以利用这些函数式接口的有效Lambda 表达式:
+ * (1) T->R
+ * (2) (int, int)->int
+ * (3) T->void
+ * (4) ()->T
+ * (5) (T, U)->R
+ */
+public class Java8InActionTest extends AbstractBaseTest {
+
+    @Test
+    public void testFun1() {
+        Fun1 f1 = (t) -> t.hashCode();
+        System.out.println("T -> R");
+        System.out.println(f1.whatEver("I'm T Object! return value it's my hascode! "));
+    }
+
+    @Test
+    public void testFun2() {
+        Fun2 f2 = (a, b) -> a + b + 100;
+        System.out.println("(int, int)->int");
+        System.out.println(f2.whatEver_JustASign(1, 2));
+    }
+
+    @Test
+    public void testFun3() {
+        Fun3 f3 = (t) -> System.out.println("T -> void");
+        f3.xxx("what ever value pass in ");
+    }
+
+    @Test
+    public void testFun4() {
+        Fun4<String> f4 = () -> "only String can return";
+        System.out.println(" ()->T ");
+        System.out.println(f4.aaa());
+    }
+
+    @Test
+    public void testFun5() {
+        Fun5<String,Integer,Long> f5 = (t,u) -> (long)(t.length() * u);
+        System.out.println(" (T, U)->R ");
+        System.out.println(f5.bbb("hello",10));
+    }
+
+}
+
+
+/**
+ * T->R
+ *
+ * @param <T>
+ * @param <R>
+ */
+@FunctionalInterface
+interface Fun1<T, R> {
+    R whatEver(T t);
+}
+
+/**
+ * (int, int)->int
+ */
+@FunctionalInterface
+interface Fun2 {
+    int whatEver_JustASign(int a, int b);
+}
+
+/**
+ * T->void
+ */
+@FunctionalInterface
+interface Fun3<T> {
+    void xxx(T t);
+}
+
+/**
+ * ()->T
+ */
+@FunctionalInterface
+interface Fun4<T> {
+    T aaa();
+}
+
+/**
+ * (T, U)->R
+ */
+@FunctionalInterface
+interface Fun5<T, U, R> {
+    R bbb(T t, U u);
+}
diff --git a/src/main/java/com/rice/java8/samples/test/AbstractBaseTest.java b/src/main/java/com/rice/java8/samples/test/AbstractBaseTest.java
@@ -26,6 +26,6 @@ public void printCurrentMethod(String methodComment) {
     @After
     @Override
     public void afterDone() {
-        System.out.println(getClass() + ", afterDone executed! ");
+        System.out.println(getClass() + ", afterDone executed! \n\n");
     }
 }

Original file line number	Diff line number	Diff line change
`@@ -26,6 +26,6 @@ public void printCurrentMethod(String methodComment) {`
`26`	`26`	`@After`
`27`	`27`	`@Override`
`28`	`28`	`public void afterDone() {`
`29`		`- System.out.println(getClass() + ", afterDone executed! ");`
	`29`	`+ System.out.println(getClass() + ", afterDone executed! \n\n");`
`30`	`30`	`}`
`31`	`31`	`}`