// innerclasses/Callbacks.java // Using inner classes for callbacks

最新推荐文章于 2021-09-05 12:44:32 发布

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本文通过实例演示了如何利用Java内部类实现回调机制。通过定义接口`Incrementable`及其实现类`Callee1`和`Callee2`，展示了简单实现与复杂场景下内部类的使用方式。

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// innerclasses/Callbacks.java
// Using inner classes for callbacks
package innerclasses;
interface Incrementable{
void increment();
}

// Very simple to just implement the interface
class Callee1 implements Incrementable {
private int i = 0;
public void increment() {
    i++;
    System.out.println(i);
}
}


class MyIncrement {
public void increment() {System.out.println("Other operation");}
static void f(MyIncrement mi) {mi.increment();}
}

// If your class must implement increment() in
// some other way, you must use an inner class:
class Callee2 extends MyIncrement {
private int i=0;
public void increment() {
  super.increment();
  i++;
  System.out.println(i);
}

private class Closure implements Incrementable {
  public void increment() {
    // Specify outer-class method, otherwise
    // you'd get an infinite recursion
   Callee2.this.increment();
   }
}

Incrementable getCallbackReference() {
     return new Closure();
}

}

class Caller {
private Incrementable callbackReference;
Caller(Incrementable cbh) {callbackReference = cbh;}
void go() {callbackReference.increment();}
}



public class Callbacks {
public static void main(String[] args) {
   Callee1 c1 = new Callee1();
   Callee2 c2 = new Callee2();
   MyIncrement.f(c2);
                     //Other operation
         //1
   Caller caller1 = new Caller(c1);
   Caller caller2 = new Caller(c2.getCallbackReference());
   caller1.go();
                    //1
   caller1.go();    //2

   caller2.go();   //Other operation
                   //2