public abstract class Beverage { protected String Description; public String getDescription(){ return Description; } public abstract int cost(); } public class Espresso extends Beverage{ public int cost(){ return 2; } public Espresso(){ Description = "Espresso"; } } abstract class CondimentDecorator extends Beverage{ public abstract String getDescription(); } public class Mocha extends CondimentDecorator{ Beverage beverage; public Mocha(Beverage beverage){ this.beverage=beverage; } @Override public String getDescription() { return beverage.getDescription()+", Mocha "; } @Override public int cost() { return beverage.cost()+0.5; } public Beverage remove(Beverage b) { return b; } } ...
还有更多的装饰品,比如牛奶,大豆......等咖啡,比如HouseBlend ......等。
如果我在物体上有摩卡牛奶装饰器,我想删除“摩卡咖啡”'装饰。
Beverage beverage = new Mocha(new Espresso());
beverage = new Milk(beverage);
编辑: 方案是
客户已添加Expresso与摩卡咖啡和牛奶。
现在,Expresso装饰着摩卡咖啡和牛奶。
突然间,客户想要用Whip替换mocha。
答案 0 :(得分:1)
你必须自己提供逻辑,例如:
CondimentDecorator#removeCondiment(Class <? extends CondimentDecorator>)
让该方法检查它是否包装该类的CondimentDecorator,并直接引用包装的Beverage,绕过装饰器移除。在包装的Beverage上递归调用它包装的装饰器不匹配。
答案 1 :(得分:1)
如果不编写自定义装饰器来处理这个问题,你就不能。除了删除装饰器,您可以重新创建饮料减去Mocha
装饰器
beverage = new Milk(new Espresso());