// : c08:Callbacks.java
// Using inner classes for callbacks
// From 'Thinking in Java, 3rd ed.' (c) Bruce Eckel 2002
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
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 {
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;
private void incr() {
i++;
System.out.println(i);
}
private class Closure implements Incrementable {
public void increment() {
incr();
}
}
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();
caller1.go();
caller2.go();
caller2.go();
}
} ///:~