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.java
Toast.javapublic 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.java
Cheese.javapublic 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: