设计模式-装饰者

定义：动态地将责任附加到对象上。若要扩展功能，装饰者提供了比继承更有弹性的替代方案。

UML图示：

代码示例：以我最爱吃的冰淇淋为例

/**定义冰淇淋抽象类*/

public abstract class Ice {

//描述

    public String desctription = "unkonw";

    //获取描述

    public abstract String getDestription();

    //计费

    public abstract double cost();

    //打印

    public void print(){

        System.out.println(getDestription() + " / " + cost());

    }

}

 

/**牛奶冰淇淋*/

public class MilkIce extends Ice{

    public MilkIce() {

        // TODO Auto-generated constructor stub

        desctription = "milk";

    }

    @Override

    public double cost() {

        // TODO Auto-generated method stub

        return 2.0d;

    }

    @Override

    public String getDestription() {

        // TODO Auto-generated method stub

        return desctription;

    }

}

 

/**

* 定义冰淇淋装饰者*/

public abstract class IceDecorator extends Ice{

    protected Ice mIce = null;

    public IceDecorator(Ice ice) {

        // TODO Auto-generated constructor stub

        mIce = ice;

    }

}

 

/**草莓佐料*/

public class StrawberryDecorator extends IceDecorator{

    public StrawberryDecorator(Ice ice) {

        super(ice);

        // TODO Auto-generated constructor stub

    }

    @Override

    public String getDestription() {

        // TODO Auto-generated method stub

        return mIce.getDestription() + "Strawberry";

    }

    @Override

    public double cost() {

        // TODO Auto-generated method stub

        return mIce.cost() + 0.5d;

    }

}

 

/**巧克力佐料*/

public class ChocolateDecorator extends IceDecorator{

    public ChocolateDecorator(Ice ice) {

        super(ice);

        // TODO Auto-generated constructor stub

    }

    @Override

    public String getDestription() {

        // TODO Auto-generated method stub

        return mIce.getDestription() + "chocolate";

    }

    @Override

    public double cost() {

        // TODO Auto-generated method stub

        return mIce.cost() + 0.8d;

    }

}

 

public class Main {

    public static void main(String[] args) {

        Ice strawberry_milk = new MilkIce();//定义牛奶草莓冰淇淋

        Ice chocolate_milk = new MilkIce();//定义牛奶巧克力冰淇淋

        strawberry_milk = new StrawberryDecorator(strawberry_milk);//加草莓装饰

        chocolate_milk = new ChocolateDecorator(chocolate_milk);//加巧克力装饰

        strawberry_milk.getDestription();

        strawberry_milk.cost();

        chocolate_milk.getDestription();

        chocolate_milk.cost();

        

        strawberry_milk.print();

        chocolate_milk.print();

    }

}

打印结果：

milkStrawberry / 2.5

milkchocolate / 2.8