设计模式之装饰模式

1、装饰模式简述

装饰模式以对客户端透明的方式给一个对象附加上更多的责任，可以在不需要创造更多子类的情况下，将对象的功能加以扩展。装饰模式包含如下角色：

Component: 抽象构件
ConcreteComponent: 具体构件
Decorator: 抽象装饰类
ConcreteDecorator: 具体装饰类

2、UML类图

3、代码实现

/**
 * 饮料接口
 * @author Administrator
 *
 */
public interface Beverage {
	//返回商品描述
	public String getDescription();
	//返回价格
	public double getPrice();
}



public class CoffeeBean1 implements Beverage {
	private String description = "选了第一种咖啡豆";
	@Override
	public String getDescription() {
		return description;
	}
	@Override
	public double getPrice() {
		return 50;
	}
}


public class CoffeeBean2 implements Beverage {
	private String description = "第二种咖啡豆！";
	@Override
	public String getDescription() {
		return description;
	}
 
	@Override
	public double getPrice() {
		return 100;
	}
}

// 装饰器类
public class Decorator implements Beverage {
	private String description = "我只是装饰器，不知道具体的描述";
	@Override
	public String getDescription() {
		return description;
	}
	@Override
	public double getPrice() {
		return 0;		//价格由子类来决定
	}
}


// 咖啡加入牛奶
public class Milk extends Decorator{
	private String description = "加了牛奶！";
	private Beverage beverage = null;
	public Milk(Beverage beverage){
		this.beverage = beverage;
	}
	public String getDescription(){
		return beverage.getDescription()+"\n"+description;
	}
	public double getPrice(){
		return beverage.getPrice()+20;	
	}
}


public class Test {
 
	public static void main(String[] args) {
		Beverage beverage = new CoffeeBean1();	
		beverage = new Mocha(beverage);		
		
	}