装饰者模式：
动态的将职责附加到对象上。
系统描述：购买咖啡的系统，购买咖啡时可以加入各种调料，然后结账的时候算上咖啡和调料的钱的总和。
总的饮料抽象类Beverage.java
package cn.beverage.demo;
/**
* 饮料抽象类
*
* @author wy
*
*/
public abstract class Beverage {
String desc = "unknow Beverage";
public String getDesc() {
return this.desc;
}
public abstract double cost();
}
調料抽象類:Condiment.java：装饰者类必须继承最上层的饮料抽象类。
package cn.beverage.demo;
/**
* 調料抽象類，装饰者类
*
* @author wy
*
*/
public abstract class Condiment extends Beverage {
public abstract String getDesc();
}
2个被装饰类：被装饰类基础最上层的饮料抽象类
package cn.beverage.demo;
/**
* 被装饰的类
*
* @author wy
*
*/
public class Espresso extends Beverage {
public Espresso() {
this.desc = "濃縮咖啡";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return 1.99;
}
}package cn.beverage.demo;
/**
* 被装饰的类
*
* @author wy
*
*/
public class HouseBlend extends Beverage {
public HouseBlend() {
this.desc = "首选咖啡";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return 0.89;
}
}
再添加两个装饰者：
package cn.beverage.demo;
/**
* 裝飾者
*
* @author wy
*
*/
public class Mocha extends Condiment {
private Beverage beverage;
public Mocha(Beverage beverage) {
this.beverage = beverage;
}
@Override
public String getDesc() {
// TODO Auto-generated method stub
return beverage.getDesc() + ",摩卡";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return 0.20 + beverage.cost();
}
}
package cn.beverage.demo;
/**
* 裝飾者
*
* @author wy
*
*/
public class Whip extends Condiment {
private Beverage beverage;
public Whip(Beverage beverage) {
this.beverage = beverage;
}
@Override
public String getDesc() {
// TODO Auto-generated method stub
return beverage.getDesc() + ",whip ";
}
@Override
public double cost() {
// TODO Auto-generated method stub
return 10 + beverage.cost();
}
}
测试方法：
package cn.beverage.demo;
public class Test {
public static void main(String[] args) {
Beverage beverage = new Espresso();
beverage = new Mocha(beverage);
System.out.println(beverage.getDesc() + " : " + beverage.cost());
Beverage beverage2 = new HouseBlend();
//用摩卡装饰beverage2
beverage2 = new Mocha(beverage2);
System.out.println(beverage2.getDesc() + " : " + beverage2.cost());
Beverage beverage3 = new Espresso();
//用摩卡装饰beverage3
beverage3 = new Mocha(beverage3);
//再用whip装饰beverage3
beverage3 = new Whip(beverage3);
System.out.println(beverage3.getDesc() + " : " + beverage3.cost());
}
}
输出结果：
濃縮咖啡,摩卡 : 2.19 首选咖啡,摩卡 : 1.09 濃縮咖啡,摩卡,whip : 12.19
