装饰着模式（decorator）
一下代码就是运用了装饰者模式：

package com.base;public abstract class Beverage {public   String description = "Unknown Beverage";public String getDescription(){return description;}public abstract double cost();}

package com.base;public abstract class CondimentDecorator extends Beverage {public abstract String getDescription();}

package com.decorated;import com.base.Beverage;public class DarkRoast extends Beverage {public DarkRoast() {description = "Dark Roast Coffee";} public double cost() {return 0.99;}}

package com.decorated;import com.base.Beverage;public class Espresso extends Beverage {public Espresso(){description = "Espresso";}@Overridepublic double cost() {return 1.99;}}

package com.decorated;import com.base.Beverage;public class HouseBlend extends Beverage {public HouseBlend(){description = "House Blend Coddee";}@Overridepublic double cost() {return 0.89;}}

package com.decorator;import com.base.Beverage;import com.base.CondimentDecorator;public class Mocha extends CondimentDecorator {Beverage beverage;public Mocha(Beverage beverage){this.beverage= beverage;}@Overridepublic String getDescription() {return beverage.getDescription()+", Mocha";}@Overridepublic double cost() {return 0.20+beverage.cost();}}

package com.decorator;import com.base.Beverage;import com.base.CondimentDecorator;public class Soy extends CondimentDecorator {Beverage beverage;public Soy(Beverage beverage) {this.beverage = beverage;}public String getDescription() {return beverage.getDescription() + ", Soy";}public double cost() {return 0.15 + beverage.cost();}}

package com.decorator;import com.base.Beverage;import com.base.CondimentDecorator;public class Whip extends CondimentDecorator {Beverage beverage; public Whip(Beverage beverage) {this.beverage = beverage;} public String getDescription() {return beverage.getDescription() + ", Whip";} public double cost() {return 0.10 + beverage.cost();}}

package com.test;import com.base.Beverage;import com.decorated.DarkRoast;import com.decorated.Espresso;import com.decorated.HouseBlend;import com.decorator.Mocha;import com.decorator.Soy;import com.decorator.Whip;public class StarBuzzCoffee {public static void main(String args[]) {Beverage beverage = new Espresso();System.out.println(beverage.getDescription() + " $" + beverage.cost()); Beverage beverage2 = new DarkRoast();beverage2 = new Mocha(beverage2);beverage2 = new Mocha(beverage2);beverage2 = new Whip(beverage2);System.out.println(beverage2.getDescription() + " $" + beverage2.cost()); Beverage beverage3 = new HouseBlend();beverage3 = new Soy(beverage3);beverage3 = new Mocha(beverage3);beverage3 = new Whip(beverage3);System.out.println(beverage3.getDescription() + " $" + beverage3.cost());}}

运行结果为：

Espresso $1.99Dark Roast Coffee, Mocha, Mocha, Whip $1.49House Blend Coddee, Soy, Mocha, Whip $1.34

运行方式为：装饰者与被装饰者都继承相同的基类，装饰者不知道其他的装饰者的存在