Default methods

slgobinath · slgobinath · commit 7579d86f1bfa · 2015-01-21T20:42:29.000+05:30
diff --git a/defaultmethods/BookDemo.java b/defaultmethods/BookDemo.java
@@ -0,0 +1,39 @@
+import java.util.*;
+
+public class BookDemo {
+    public static void main(String[] args) {
+        Book book = new Book();
+        book.add(new Chapter("Chapter 1"));
+        book.add(new Chapter("Chapter 2"));
+        book.add(new Chapter("Chapter 3"));
+        for(Chapter ch : book) {
+            System.out.println(ch);
+        }
+    }
+}
+
+class Book implements Iterable<Chapter> {
+    private List<Chapter> chapters = new ArrayList<>();
+
+    public void add(Chapter chapter) {
+        this.chapters.add(chapter);
+    }
+
+    @Override
+    public Iterator<Chapter> iterator() {
+        return chapters.iterator();
+    }
+}
+
+class Chapter {
+    private String title;
+
+    public Chapter(String title) {
+        this.title = title;
+    }
+
+    @Override
+    public String toString() {
+        return this.title;
+    }
+}
diff --git a/defaultmethods/DefaultInClass.java b/defaultmethods/DefaultInClass.java
@@ -0,0 +1,9 @@
+public class DefaultInClass {
+	/*
+	* Compile time error.
+	* Cannot have default method inside a class.
+	*/
+	default void doStuff() {
+		System.out.println("Hello world");
+	}
+}
diff --git a/defaultmethods/DefaultWithoutBody.java b/defaultmethods/DefaultWithoutBody.java
@@ -0,0 +1,7 @@
+public interface DefaultWithoutBody {
+	/*
+	* Compile time error.
+	* No method body for the default method.
+	*/
+	default void doStuff();
+}
diff --git a/defaultmethods/DiamondProblem.java b/defaultmethods/DiamondProblem.java
@@ -0,0 +1,31 @@
+public class DiamondProblem {
+	public static void main(String[] args) {
+		A obj = new D();
+		obj.print();
+	}
+}
+
+interface A {
+	default void print() {
+		System.out.println("A");
+	}
+}
+
+interface B extends A {
+	default void print() {
+		System.out.println("B");
+	}
+}
+
+interface C extends A {
+	default void print() {
+		System.out.println("C");
+	}
+}
+/*
+* Compile time error.
+* Diamond problem since there is a clash in the print() methods.
+*/
+class D implements B, C {
+
+}
diff --git a/defaultmethods/DiamondSolutionOne.java b/defaultmethods/DiamondSolutionOne.java
@@ -0,0 +1,34 @@
+public class DiamondSolutionOne {
+	public static void main(String[] args) {
+		A obj = new D();
+		obj.print();
+	}
+}
+
+interface A {
+	default void print() {
+		System.out.println("A");
+	}
+}
+
+interface B extends A {
+	default void print() {
+		System.out.println("B");
+	}
+}
+
+interface C extends A {
+	default void print() {
+		System.out.println("C");
+	}
+}
+
+/*
+* The overridden method will get selected
+*/
+class D implements B, C {
+	@Override
+	public void print() {
+		System.out.println("D");
+	}
+}
diff --git a/defaultmethods/DiamondSolutionTwo.java b/defaultmethods/DiamondSolutionTwo.java
@@ -0,0 +1,37 @@
+public class DiamondSolutionTwo {
+	public static void main(String[] args) {
+		A obj = new D();
+		obj.print();
+	}
+}
+
+interface A {
+	default void print() {
+		System.out.println("A");
+	}
+}
+
+interface B extends A {
+	default void print() {
+		System.out.println("B");
+	}
+}
+
+interface C extends A {
+	default void print() {
+		System.out.println("C");
+	}
+}
+
+class P {
+	public void print() {
+		System.out.println("P");
+	}
+}
+
+/*
+* Super class provides the implementation of print() method
+*/
+class D extends P implements B, C {
+	
+}
diff --git a/defaultmethods/FinalDefaultMethod.java b/defaultmethods/FinalDefaultMethod.java
@@ -0,0 +1,9 @@
+public interface FinalDefaultMethod {
+	/*
+	* Compile time error.
+	* final and default cannot be used together.
+	*/
+	public final default void print() {
+		System.out.println("Hello world");
+	}
+}
diff --git a/defaultmethods/MultiSales.java b/defaultmethods/MultiSales.java
@@ -0,0 +1,55 @@
+public class MultiSales {
+    public static void main(String[] args) {
+        doStuff(new Pen(10.00), 5);
+        doStuff(new Book(250.00, 5.00), 2);
+    }
+
+    public static void doStuff(Sellable item, int count) {
+        double income = item.sell(count);
+        System.out.println("Income: $" + income);
+    }
+}
+
+interface Sellable {
+    double sell();
+
+    default double sell(int count) {
+        double total = 0.0;
+        for(int i = 1; i <= count; i++) {
+            total += this.sell();
+        }
+        return total;
+    }
+
+    default String toString() {
+        return "df";
+    }
+}
+
+class Book implements Sellable {
+    private double price;
+    private double discount;
+
+    public Book(double price, double discount) {
+        this.price = price;
+        this.discount = discount;
+    }
+
+    @Override
+    public double sell() {
+        return price - (price * discount / 100.00);
+    }
+}
+
+class Pen implements Sellable {
+    private double price;
+
+    public Pen(double price) {
+        this.price = price;
+    }
+
+    @Override
+    public double sell() {
+        return price;
+    }
+}
diff --git a/defaultmethods/OverrideDemo.java b/defaultmethods/OverrideDemo.java
@@ -0,0 +1,26 @@
+public class OverrideDemo {
+	public static void main(String[] args) {
+		Note note = new Note("Hello world");
+		note.read();
+	}
+}
+
+interface Readable {
+	default void read() {
+		System.out.println("Read");
+	}
+}
+
+
+class Note implements Readable {
+	private String content;
+
+	public Note(String content) {
+		this.content = content;
+	}
+
+	@Override
+	public void read() {
+		System.out.println(content);
+	}
+}
diff --git a/defaultmethods/OverrideToString.java b/defaultmethods/OverrideToString.java
@@ -0,0 +1,9 @@
+public interface OverrideToString {
+	/*
+	* Compile time error.
+	* Cannot override any methods of java.lang.Object class.
+	*/
+	public default String toString() {
+		return "Hello";
+	}
+}
diff --git a/defaultmethods/SingleSales.java b/defaultmethods/SingleSales.java
@@ -0,0 +1,43 @@
+public class SingleSales {
+    public static void main(String[] args) {
+        doStuff(new Pen(10.00));
+        doStuff(new Book(250.00, 5.00));
+    }
+
+    public static void doStuff(Sellable item) {
+        double income = item.sell();
+        System.out.println("Income: $" + income);
+    }
+}
+
+interface Sellable {
+    double sell();
+}
+
+class Book implements Sellable {
+    private double price;
+    private double discount;
+
+    public Book(double price, double discount) {
+        this.price = price;
+        this.discount = discount;
+    }
+
+    @Override
+    public double sell() {
+        return price - (price * discount / 100.00);
+    }
+}
+
+class Pen implements Sellable {
+    private double price;
+
+    public Pen(double price) {
+        this.price = price;
+    }
+
+    @Override
+    public double sell() {
+        return price;
+    }
+}
diff --git a/defaultmethods/StaticDefaultMethod.java b/defaultmethods/StaticDefaultMethod.java
@@ -0,0 +1,9 @@
+public interface StaticDefaultMethod {
+	/*
+	* Compile time error.
+	* static and default cannot be used together.
+	*/
+	public static default void print() {
+		System.out.println("Hello world");
+	}
+}
diff --git a/defaultmethods/SynchronizedDefaultMethod.java b/defaultmethods/SynchronizedDefaultMethod.java
@@ -0,0 +1,9 @@
+public interface SynchronizedDefaultMethod {
+	/*
+	* Compile time error.
+	* synchronized and default cannot be used together.
+	*/
+	public synchronized default void print() {
+		System.out.println("Hello world");
+	}
+}
