装饰器模式是在不改变原来的基础上对原有功能的增强。

类图如下:

装饰器模式类图.jpg

示例代码如下：

public class PackDecorator implements IPack {
    private IPack pack;
    public PackDecorator(IPack pack) {
        this.pack = pack;
    }
    @Override
    public void packFruit() {
        pack.packFruit();
    }
}

public class CheckPackDecorator extends PackDecorator {
    public CheckPackDecorator(IPack pack) {
        super(pack);
        check();
    }
    //增加功能
    public void check(){
        System.out.println("检查防伪----");
    }
}


public class ReinForcePackDecorator extends PackDecorator {
    public ReinForcePackDecorator(IPack pack) {
        super(pack);
        reinForce();
    }
    //增加加固功能
    public void reinForce(){
        System.out.println("打包加固-----");
    }
}
public class SpeedPackDecorator extends PackDecorator {
    public SpeedPackDecorator(IPack pack) {
        super(pack);
        addSpeed();
    }
    public void addSpeed(){
        System.out.println("请加速-----");
    }
}

public class DecoratorTest {
    public static void main(String[] args) {
        AbstractFactory factory = new AppleFactory();
        Fruit fruit = factory.getFruit()
        IPack pack = factory.getPack();

        pack = new CheckPackDecorator(pack);//增加check
        pack = new ReinForcePackDecorator(pack);
        pack = new SpeedPackDecorator(pack);
        pack.packFruit();
    }
}