装饰模式

1.概念

动态地为对象附加上额外的职责 其目的是包装一个对象，从而可以在运行时动态添加新的职责。每个装饰器都可以包装另一个装饰器，这样理论上来说可以对目标对象进行无限次的装饰。

2.装饰器类图

3.代码

一个早餐店经营两种主食：汉堡和吐司，一段时间后需要加个配料。 主要思路是：以主食（汉堡、吐司）为主体，然后再运行时以配料（火腿、起司）装饰为主食。其UML图为：(1)抽象构建类————Breakfast.java，早餐的抽象父类

public abstract class Breakfast { public String description="未知"; public String getDescription(){ return description; } public abstract Double cost(); }

(2)抽象装饰类————CondimentDecorator.java，是早餐抽象类的子类

public abstract class CondimentDecorator extends Breakfast{ Breakfast myfood; public CondimentDecorator(Breakfast myfood){ this.myfood=myfood; } @Override public String getDescription(){ return myfood.getDescription(); } @Override public Double cost(){ return myfood.cost(); } }

(3)具体构建类————Toast.java、Burger.javaToast.java

public class Toast extends Breakfast { public Toast(){ description="吐司"; } public Double cost(){ return 10d; } }

Burger.java

public class Burger extends Breakfast { public Burger(){ description="汉堡"; } @Override public Double cost(){ return 15d; } }

(4)具体装饰类————Cheese.java、Ham.javaCheese.java

public class Cheese extends CondimentDecorator { public Cheese(Breakfast myfood) { super(myfood); } @Override public Double cost() { return super.cost() + 5; } @Override public String getDescription() { return super.getDescription() + ",起司"; } }

Ham.java

public class Ham extends CondimentDecorator { public Ham(Breakfast myfood) { super(myfood); } @Override public Double cost() { return super.cost() + 10; } @Override public String getDescription() { return super.getDescription() + ",火腿"; } }

(5)客户端测试类

public class Decorator { public static void main(String args[]) { Breakfast breakfast1 = new Toast(); System.out.println("您点的餐点为：" + breakfast1.getDescription() + "。价格为：" + breakfast1.cost()); Breakfast breakfast2 = new Toast(); breakfast2 = new Ham(breakfast2); breakfast2 = new Ham(breakfast2); System.out.println("您点的餐点为：" + breakfast2.getDescription() + "。价格为：" + breakfast2.cost()); Breakfast breakfast3 = new Burger(); breakfast3 = new Ham(breakfast3); breakfast3 = new Cheese(breakfast3); breakfast3 = new Cheese(breakfast3); System.out.println("您点的餐点为：" + breakfast3.getDescription() + "。价格为：" + breakfast3.cost()); } }

结果

您点的餐点为：吐司。价格为：10.0 您点的餐点为：吐司,火腿,火腿。价格为：30.0 您点的餐点为：汉堡,火腿,起司,起司。价格为：35.0

详细见：Java设计模式

转载于:https://www.cnblogs.com/w1570631036/p/6830887.html

相关资源：数据结构—成绩单生成器