81 lines
1.7 KiB
Java
81 lines
1.7 KiB
Java
// innerclasses/Callbacks.java
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// (c)2016 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://mindviewinc.com/Books/OnJava/ for more book information.
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// Using inner classes for callbacks
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package innerclasses;
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interface Incrementable {
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void increment();
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}
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// Very simple to just implement the interface:
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class Callee1 implements Incrementable {
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private int i = 0;
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@Override
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public void increment() {
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i++;
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System.out.println(i);
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}
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}
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class MyIncrement {
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public void increment() {
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System.out.println("Other operation");
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}
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static void f(MyIncrement mi) { mi.increment(); }
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}
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// If your class must implement increment() in
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// some other way, you must use an inner class:
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class Callee2 extends MyIncrement {
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private int i = 0;
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@Override
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public void increment() {
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super.increment();
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i++;
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System.out.println(i);
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}
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private class Closure implements Incrementable {
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@Override
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public void increment() {
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// Specify outer-class method, otherwise
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// you'd get an infinite recursion:
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Callee2.this.increment();
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}
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}
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Incrementable getCallbackReference() {
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return new Closure();
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}
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}
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class Caller {
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private Incrementable callbackReference;
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Caller(Incrementable cbh) { callbackReference = cbh; }
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void go() { callbackReference.increment(); }
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}
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public class Callbacks {
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public static void main(String[] args) {
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Callee1 c1 = new Callee1();
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Callee2 c2 = new Callee2();
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MyIncrement.f(c2);
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Caller caller1 = new Caller(c1);
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Caller caller2 = new Caller(c2.getCallbackReference());
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caller1.go();
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caller1.go();
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caller2.go();
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caller2.go();
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}
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}
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/* Output:
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Other operation
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1
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1
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2
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Other operation
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2
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Other operation
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3
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*/
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