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装饰者模式：动态的将新功能附加到对象上，在对象功能扩展方面，它比继承更有弹性。

一、咖啡馆订单项目

1)、咖啡种类 : Espresso、ShortBlack、LongBlack、Decaf

下面这个方案会类爆炸：

二、装饰者模式

1、Drink抽象类

public abstract class Drink {	public String description="";	private float price=0f;;	public void setDescription(String description){		this.description=description;	}	public String getDescription(){		return description+"-"+this.getPrice();	}	public float getPrice(){		return price;	}	public void setPrice(float price){		this.price=price;	}	public abstract float cost();	}

2、Coffee类及其实现类

1）、Coffee基类

public  class Coffee extends Drink {	@Override	public float cost() {		return super.getPrice();	}}

2）、Decaf类

public class Decaf extends Coffee {	public Decaf()	{		super.setDescription("Decaf");		super.setPrice(3.0f);	}}

3）、Espresso类

public class Espresso extends Coffee{	public Espresso(){		super.setDescription("Espresso");		super.setPrice(4.0f);	}}

4）、LongBlack类

public class LongBlack extends Coffee{	public LongBlack(){		super.setDescription("LongBlack");		super.setPrice(6.0f);	}}

3、Decorator类及其实现类

1）、Decorator基类

public  class Decorator extends Drink {	private Drink Obj;    		public Decorator(Drink Obj){		this.Obj=Obj;	};		@Override	public float cost() {				return super.getPrice()+Obj.cost();	}	@Override	public String getDescription(){		return super.description+"-"+super.getPrice()+"&&"+Obj.getDescription();	}	}

2）、Chocolate类

public class Chocolate extends Decorator {	public Chocolate(Drink Obj) {				super(Obj);		super.setDescription("Chocolate");		super.setPrice(3.0f);	}}

3）、Milk类

public class Milk extends Decorator {	public Milk(Drink Obj) {				super(Obj);		super.setDescription("Milk");		super.setPrice(2.0f);	}}

4、Decorator类及其实现类

public class CoffeeBar {	public static void main(String[] args) {				Drink order;		order=new Decaf();		System.out.println("order1 price:"+order.cost());		System.out.println("order1 desc:"+order.getDescription());				System.out.println("****************");				order=new LongBlack();   // 一杯黑咖啡		order=new Milk(order);    //  一杯加牛奶的黑咖啡		order=new Chocolate(order);   //   一杯加Chocolate加牛奶的黑咖啡		order=new Chocolate(order);  //    一杯加两份Chocolate加牛奶的黑咖啡		System.out.println("order2 price:"+order.cost());		System.out.println("order2 desc:"+order.getDescription());		}}

三、java中装饰者模式