【JavaSE】java實現閉包與回撥

java實現閉包與回撥

closure是一個可被呼叫的物件，它記錄一些資訊，這些資訊來自於建立它的作用域。
通過內部類實現閉包是java提供優良解決方案。參考《Think in java》p207

Callee1直接實現Increment介面
Callee2通過內部類實現介面

package com.huat.callback;

interface Incrementable {
    void increment();
}

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 operration");
    }

    static void f(MyIncrement mi) {
    mi.increment();

    }
}


class Callee2 extends MyIncrement {
    private int i = 0;
    public void increment() {
    super.increment();
    i++;
    System.out.println(i);
    }

    private class Closure implements Incrementable {

    @Override
    public void increment() {
        // TODO Auto-generated method stub
        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();
    caller1.go();
    caller2.go();
    caller2.go();

    }
}