装饰模式使用被装饰类的一个子类的实例，把客户端的调用委派到被装饰类，装饰模式的关键在于这种扩展是完全透明的。
/**
* 装饰器模式，(装饰者和被装饰者的类型必须是一样的，拥有相同的超类或者相同的接口)
*/
public abstract class Beverage {
protected String description = "unknow beverage";
public String getDescription() {
return description;
}
public abstract double cost();
}
//装饰者
public abstract class CondimentDecorator extends Beverage {
public abstract String getDescription();
}
//被装饰者实现类
public class HouseBlend extends Beverage {
public HouseBlend() {
description = "House Blend Coffee";
}
@Override
public double cost() {
return 0.89;
}
}
//装饰者实现类
public class Mocha extends CondimentDecorator {
private Beverage beverage;
public Mocha(Beverage beverage) {
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ", Mocha";
}
@Override
public double cost() {
return 0.20 + beverage.cost();
}
}
//又一装饰者实现类
public class Whip extends CondimentDecorator {
private Beverage beverage;
public Whip(Beverage beverage) {
this.beverage = beverage;
}
@Override
public String getDescription() {
return beverage.getDescription() + ", Whip";
}
@Override
public double cost() {
return 0.10 + beverage.cost();
}
}
//测试类
public class Test {
public static void main(String[] args) {
Beverage beverage = new HouseBlend();
System.out.println(beverage.getDescription() + "\t" + beverage.cost());
Beverage beverage1 = new HouseBlend();
beverage1 = new Mocha(beverage1);
beverage1 = new Whip(beverage1);
System.out.println(beverage1.getDescription() + "\t" + beverage1.cost());
}
}
//结果：
House Blend Coffee 0.89
House Blend Coffee, Mocha, Whip 1.1900000000000002
原文：http://www.cnblogs.com/fanguangdexiaoyuer/p/5786820.html