hand first 设计模式 - 装饰者模式

所有饮料抽象类

public abstract class Beverage {

	String description = "unknown beverage";

	public String getDescription() {
		return description;
	}

	public abstract double cost();

}

装饰者抽象类

public abstract class CondimentDecorator extends Beverage {

	public abstract String getDescription();
	

}

浓咖啡

public class Espresso extends Beverage {

	public Espresso(){
		description = "Espresso";
	}
	@Override
	public double cost() {
		// TODO Auto-generated method stub
		return 1.99;
	}

}

佐料(装饰者)摩卡类

public class Mocha extends CondimentDecorator {

	Beverage beverage;
	
	public Mocha(Beverage beverage){
		this.beverage = beverage;
	}
	@Override
	public String getDescription() {
		// TODO Auto-generated method stub
		System.out.println(beverage.getDescription());
		
		return beverage.getDescription()+",Mocha";
	}

	@Override
	public double cost() {
		// TODO Auto-generated method stub
		return .20 +beverage.cost();
	}

}

public class StarbuzzCoffee {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		//单纯的咖啡
		Beverage beverage = new Espresso();
		
                   //加入摩卡的咖啡
		beverage = new Mocha(beverage);
		
		System.out.println(beverage.getDescription()+" $ "+beverage.cost());
}

}

设计原则
对扩展开放,对修改关闭