装饰者模式

Source:被装饰对象
Decorator：装饰者父类，继承Source。该对象中有一个source实例
DecoratorA： 具体的装饰者。继承Decorator，自己的方法+supper中的方法。
DecoratorB： 具体的装饰者。继承Decorator，自己的方法+supper中的方法。

public class Source {
    public void sing(){
        System.out.println("sing..");
    }
}

public class Decorate extends Source {

    private Source source;

    public Decorate(Source source) {
        this.source = source;
    }

    @Override
    public void sing() {
        source.sing();
    }
}

public class DecorateA extends Decorate {

    public DecorateA(Source source) {
        super(source);
    }

    @Override
    public void sing() {
        dance();
        super.sing();
    }

    public void dance() {
        System.out.println("dance...");
    }
}

public class DecorateB extends Decorate {

    public DecorateB(Source source) {
        super(source);
    }

    @Override
    public void sing() {
        cry();
        super.sing();
    }

    public void cry() {
        System.out.println("cry...");
    }
}

public class Client {
    public static void main(String[] args) {
        Source source = new Source();
        Source decorateA = new DecorateB(new DecorateA(source));
        decorateA.sing();
    }
}