装饰者模式(Decorator Pattern)_Java
?问题
?我开了一家蛋糕店，蛋糕最普通的是面包奶油蛋糕(MilkCake)，你可以根据自己的喜好，在这个普通的蛋糕上添加你喜欢的一些装饰，我们提供的有：
草莓：Strawberry=$8
巧克力：Chocolate=$11
苹果：Apple=$5
橘子：Orange=$3
....
普通蛋糕：$100
现在我需要做一个草莓巧克力蛋糕，需要多少钱？
方案一
//MilkCake类package com.pattern.decorator;public class MilkCake {private float milkCake=100;public float cost(){return milkCake;}}?//StrawberryChocolateCakepackage com.pattern.decorator;public class StrawberryChocolateCake extends MilkCake{private float strawberry=8;//草莓价格private float chocolate=11;//巧克力的价格@Overridepublic float cost() {return super.cost()+strawberry+chocolate;//加上草莓巧克力后的蛋糕的价格}}?//Testpackage com.pattern.decorator;public class Test {public static void main(String[] args) {StrawberryChocolateCake strawberryChocolateCake=new StrawberryChocolateCake();float money=strawberryChocolateCake.cost();System.out.println(money);}}?问题
有人想要一个巧克力奶油蛋糕，我需要改源码
草莓价格改了，我还需要改源码
...
这样的话，太折腾人了
问题的解决
装饰者模式
动态的将责任附加到对象上，如要扩展，装饰者提供了比继承更有弹性的替代方案
方案二
package com.pattern.decorator1;public interface Cake {public abstract float cost();}?
package com.pattern.decorator1;/** * 基本的蛋糕-牛奶蛋糕-100元哟！ */public class MilkCake implements Cake{private float milkCake=100;@Overridepublic float cost() {return milkCake;}}?
package com.pattern.decorator1;/** * 蛋糕装饰者，如果你是装饰者，你就需要继承此类方能给蛋糕装饰 */public abstract class CakeDecorator implements Cake{}?
package com.pattern.decorator1;/** * 草莓蛋糕是装饰普通蛋糕的，继承CakeDecorator */public class StrawberryCake extends CakeDecorator{private Cake cake;//标识装饰给那一块蛋糕的private float strawberry=8;//草莓的价格public StrawberryCake(){}/** * 如果需要草莓来装饰蛋糕，就把你的蛋糕放进来吧！！！ */public StrawberryCake(Cake cake){this.cake=cake;}/** * 算出草莓装饰后的蛋糕的总价 */@Overridepublic float cost() {return cake.cost()+strawberry;}}?
package com.pattern.decorator1;/** * 巧克力蛋糕是装饰普通蛋糕的，继承CakeDecorator */public class ChocolateCake extends CakeDecorator{private Cake cake;//标识装饰给那一块蛋糕的private float chocolate=11;//巧克力的价格public ChocolateCake(){}/** * 如果需要巧克力来装饰蛋糕，就把你的蛋糕放进来吧！！！ */public ChocolateCake(Cake cake){this.cake=cake;}/** * 算出草莓装饰后的蛋糕的总价 */@Overridepublic float cost() {return cake.cost()+chocolate;}}?
package com.pattern.decorator1;public class Test {public static void main(String[] args) {MilkCake cake=new MilkCake();float money1=cake.cost();System.out.println(money1);//普通蛋糕100StrawberryCake strawberryCake=new StrawberryCake(cake);float money2=strawberryCake.cost();System.out.println(money2);//草莓蛋糕108ChocolateCake chocolateCake=new ChocolateCake(strawberryCake);float money3=chocolateCake.cost();System.out.println(money3);//巧克力草莓蛋糕119}}?
Java.io中的装饰者模式
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