创建内部类
1 /** 2 * 内部类创建 3 * @author jing.ming 4 * 5 */ 6 public class Parcel1 { 7 class Contents{ 8 private int i=11; 9 public int value(){ 10 return i ; 11 } 12 } 13 class Destination{ 14 private String label; 15 Destination(String whereTo){ 16 label = whereTo ; 17 } 18 String readLabel(){ 19 return label ; 20 } 21 } 22 public Destination to(String s){ 23 return new Destination( s); 24 } 25 public Contents contents(){ 26 return new Contents() ; 27 } 28 public void ship(){ 29 Parcel1 parcel2 = new Parcel1(); 30 Parcel1.Contents c= parcel2.contents(); 31 Parcel1.Destination d = parcel2.to( "===ShiYan===") ; 32 System. out.println( d.readLabel()) ; 33 System. out.println( c.value()) ; 34 } 35 public static void main(String[] args){ 36 Parcel1 parcel= new Parcel1(); 37 parcel.ship(); 38 } 39 }
1 public class Sequence { 2 3 private Object[] items ; 4 private int next = 0 ; 5 public Sequence( int size){ 6 items = new Object[ size] ; 7 } 8 public void add(Object x){ 9 if( next< items. length){ 10 items[ next++] = x ; 11 } 12 } 13 14 private class SequenceSelector implements Selector{ 15 16 private int i = 0 ; 17 @Override 18 public boolean isEnd() { 19 return i== items. length ; 20 } 21 22 @Override 23 public Object currentObj() { 24 return items[ i] ; 25 } 26 27 @Override 28 public void next() { 29 if( i< items. length) i++ ; 30 } 31 32 } 33 34 public Selector selector(){ 35 return new SequenceSelector(); 36 } 37 38 public static void main(String[] args){ 39 Sequence sequence = new Sequence(10) ; 40 for( int i =0 ; i<10; i++){ 41 sequence.add(Integer. toString(i)); 42 } 43 Selector selector = sequence.selector() ; 44 while(! selector.isEnd()){ 45 System. out.println( selector.currentObj()); 46 selector.next(); 47 } 48 } 49 } 50
1 /** 2 * 使用.this，获得外部类对象的引用 3 * @author jing.ming 4 * 5 */ 6 public class DotThis { 7 8 void f(){ 9 System. out.println( "DotThis.f()"); 10 } 11 public class Inner{ 12 public DotThis outer(){ 13 return DotThis. this ; 14 } 15 } 16 public Inner inner(){ 17 return new Inner(); 18 } 19 20 public static void main(String[] args){ 21 DotThis dt = new DotThis() ; 22 DotThis.Inner dti = dt.inner(); 23 dti.outer().f(); 24 } 25 }
1 /** 2 * 创建内部类对象，使用.new语法 3 * @author jing.ming 4 * 5 */ 6 public class DotNew { 7 8 public class Inner{ 9 10 } 11 public static void main(String[] args){ 12 DotNew dn = new DotNew() ; 13 DotNew.Inner dti = dn. new Inner(); 14 } 15 }
1 /** 2 * 内部类在接口中的重要应用 3 * 4 * @author jing.ming 5 * 6 */ 7 class Parcel4 { 8 private class PContents implements Contents { 9 private int i = 11; 10 @Override 11 public int value() { 12 return i; 13 } 14 } 15 protected class PDestination implements Destination { 16 private String label; 17 private PDestination(String whereTo) { 18 label = whereTo; 19 } 20 21 @Override 22 public String readLable() { 23 return label; 24 } 25 } 26 public Destination destination(String s) { 27 return new PDestination( s); 28 } 29 public Contents contents() { 30 return new PContents(); 31 } 32 } 33 34 public class TestParcel1 { 35 public static void main(String[] args) { 36 Parcel4 p = new Parcel4(); 37 Contents c = p.contents(); 38 Destination d = p.destination( "ShiYan"); 39 } 40 }
1 /** 2 * 局部内部类 3 * 4 * @author jing.ming 5 * 6 */ 7 public class Parcel5 { 8 public Destination destination(String s) { 9 class PDestination implements Destination { 10 private String label; 11 private PDestination(String whereTo) { 12 label = whereTo; 13 } 14 @Override 15 public String readLable() { 16 return label; 17 } 18 } 19 return new PDestination( s); 20 } 21 public static void main(String[] args) { 22 Parcel5 p = new Parcel5(); 23 Destination d = p.destination( "ShiYan"); 24 } 25 }
1 /** 2 * 在作用域内嵌入内部类 3 * @author jing.ming 4 * 5 */ 6 public class Parcel6 { 7 private void internalTracking( boolean b){ 8 if( b){ 9 class TrackingSlip{ 10 private String id ; 11 TrackingSlip(String s){ 12 id = s ; 13 } 14 String getSlip(){ 15 return id ; 16 } 17 } 18 TrackingSlip ts = new TrackingSlip( "slip") ; 19 String s = ts.getSlip(); 20 } 21 //can‘t use it here!out of scope 22 //TrackingSlip ts = new TrackingSlip("x") ; 23 } 24 public void track (){ 25 internalTracking( true) ; 26 } 27 public static void main(String[] args) { 28 Parcel6 p = new Parcel6() ; 29 p. track(); 30 } 31 32 }
1 /** 2 * 匿名内部类使用 3 * @author jing.ming 4 * 5 */ 6 public class Parcel7 { 7 public Contents contents(){ 8 return new Contents(){ 9 private int i = 11 ; 10 public int value(){ 11 return i ; 12 } 13 }; 14 } 15 public static void main(String[] args) { 16 Parcel7 p = new Parcel7(); 17 Contents c = p.contents() ; 18 } 19 } 20 等价与下面的实现： 21 public class Parcel7b { 22 class MyContents implements Contents{ 23 private int i = 11 ; 24 public int value(){ 25 return i ; 26 } 27 } 28 //Contents c = new MyContents() ; 29 public Contents contents(){ 30 return new MyContents() ; 31 } 32 public static void main(String[] args) { 33 Parcel7 p = new Parcel7(); 34 Contents c = p.contents() ; 35 36 } 37 } 38
1 public class Wrapping { 2 private int i ; 3 public Wrapping( int x){ 4 i = x ; 5 } 6 public int value(){ 7 return i ; 8 } 9 } 10 //// 11 public class Parcel8 { 12 public Wrapping wrapping( int x){ 13 return new Wrapping( x){ 14 public int value(){ 15 return super.value()*47; 16 } 17 }; 18 } 19 public static void main(String[] args) { 20 Parcel8 p = new Parcel8() ; 21 Wrapping w = p.wrapping(10); 22 } 23 }
1 interface A{} 2 interface B{} 3 class X implements A,B{} 4 class Y implements A{ 5 B makeB(){ 6 return new B(){}; 7 } 8 } 9 public class MultiInterfaces { 10 static void takesA(A a){} 11 static void takesB(B b){} 12 13 public static void main(String[] args) { 14 X x = new X() ; 15 Y y = new Y(); 16 17 takesA(x); 18 takesB(x); 19 20 takesA(y); 21 takesB(y.makeB()); 22 } 23 }
1 package org.mj.callbackInnerclass; 2 3 interface Incrementable{void increment();} 4 class Callee1 implements Incrementable{ 5 private int i = 0 ; 6 @Override 7 public void increment() { 8 i++; 9 System.out.println("i="+i); 10 } 11 } 12 class MyIncrement{ 13 public void increment(){ 14 System.out.println("Other operation."); 15 } 16 static void f(MyIncrement mi){ 17 mi.increment(); 18 } 19 } 20 21 class Callee2 extends MyIncrement{ 22 private int i = 0 ; 23 public void increment(){ 24 super.increment(); 25 i++ ; 26 System.out.println("i="+i); 27 } 28 private class Closure implements Incrementable{ 29 @Override 30 public void increment() { 31 Callee2.this.increment(); 32 } 33 } 34 Incrementable getCallbackReference(){ 35 return new Closure() ; 36 } 37 } 38 39 class Caller{ 40 private Incrementable callbackReference ; 41 Caller(Incrementable cbh){ 42 callbackReference = cbh ; 43 } 44 void go(){ 45 callbackReference.increment(); 46 } 47 } 48 public class Callbacks { 49 public static void main(String[] args) { 50 Callee1 c1 = new Callee1() ; 51 Callee2 c2 = new Callee2() ; 52 MyIncrement.f(c2); 53 Caller caller1 = new Caller(c1) ; 54 Caller caller2 = new Caller(c2.getCallbackReference()) ; 55 caller1.go(); 56 caller1.go(); 57 caller2.go(); 58 caller2.go(); 59 } 60 61 }
运行结果：
Other operation.
i=1
i=1
i=2
Other operation.
i=2
Other operation.
i=3
这个例子进一步展示了外围内实现一个接口与内部类实现此接口之间的区别。就代码而言，Callee1是简单的解决方式。Callee2继承自Mycrement，后者已经有了一个不同的increment()方法，并且与Incrementable接口期望的increment()方法完全不相干。所以如果Callee2继承了MyIncrement，就不能为了Incrementable的用途而覆盖increment()方法，于是只能使用内部类独立的实现Incrementable。还要注意，当建立了一个内部类时，并没有在外围类的接口中添加东西，也没有修改外围类的接口。
内部类Closure实现了Incrementable，以提供一个返回Callee2的“钩子”（HOOK)——而且是一个安全的钩子，无论谁获得此Incrementable的引用，都只能调用increment(),除此之外没有其他功能（不像指针，允许你做很多事情）。
回调的价值在于它的灵活性——可以在运行时动态地决定需要调用什么方法。这样做的好处在GUI功能的实现中得到很好的体现。
原文：http://www.cnblogs.com/jsStudyjj/p/4905850.html