OnJava8-Examples/innerclasses/Callbacks.java at master · xinan-w/OnJava8-Examples · GitHub

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// innerclasses/Callbacks.java

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// Using inner classes for callbacks

// {java innerclasses.Callbacks}

package innerclasses;

interface Incrementable {

void increment();

}

// Very simple to just implement the interface:

class Callee1 implements Incrementable {

private int i = 0;

@Override 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;

@Override public void increment() {

super.increment();

i++;

System.out.println(i);

}

private class Closure implements Incrementable {

@Override public void increment() {

// Specify outer-class method, otherwise

// you'll 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);

Caller caller1 = new Caller(c1);

Caller caller2 =

new Caller(c2.getCallbackReference());

caller1.go();

caller2.go();

}

/* Output:

Other operation

OnJava8-Examples/innerclasses/Callbacks.java at master · xinan-w/OnJava8-Examples · GitHub

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