一,项目需求

咖啡馆订单项目：
1）咖啡种类：Espresso、ShortBlack、LongBlack、Decaf
2）调料：Milk、Soy、Chocolate
3）扩展性好、改动方便、维护方便

二,类的关系

装饰者模式.png

三,代码实现

1.Drink类

此类是最顶级的父类

public abstract class Drink {

    public String description="";
    private float price=0f;
    public String getDescription() {
        return description;
    }
    public void setDescription(String description) {
        this.description = description;
    }
    public float getPrice() {
        return price;
    }
    public void setPrice(float price) {
        this.price = price;
    }
    //每种饮料都有自己的价钱
    public abstract float cost();
} 

以下是咖啡的种类

1 coffee所有咖啡的父类(不含有调味剂)

/**
 * Coffee的总称 
 * 价格交给子类设置
 */
public class Coffee extends Drink{
    @Override
    public float cost() {
        return super.getPrice();
    }

}

1.1 Decaf

public class Decaf extends Coffee{

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

1.2 Espresso

public class Espresso extends Coffee{

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

1.3 LongBlack

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

1.3 ShortBlack

public class ShortBlack extends Coffee{

   public ShortBlack()
   {
       super.setDescription("ShortBlack");
       super.setPrice(5.0f);
   }
}

2.修饰类(调味)

中间的一个父类

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

2.1 Chocolate

public Chocolate(Drink obj) {
       super(obj);
       super.setDescription("Chocolate");
       super.setPrice(3.0f);
   }

2.2 Milk

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

2.3 Soy

public class Soy extends Decorator {
      public Soy(Drink Obj) {      
       super(Obj);
       super.setDescription("Soy");
       super.setPrice(1.5f);
   }
}

3.测试类

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();
        order=new Milk(order);
        order=new Chocolate(order);
        order=new Chocolate(order);
        System.out.println("order2 price:"+order.cost());
        System.out.println("order2 desc:"+order.getDescription());
        
    }

运行结果: 运行结果.png

四.重点代码分析

@Override
    public float cost() {
        System.out.println(super.getPrice());
        return super.getPrice()+obj.cost();
    }
    
    @Override
    public String getDescription()
    {
        return super.description+"-"+super.getPrice()+"&&"+obj.getDescription();
    }

实现图解如下图: 这是测试代码实现的步骤 递归调用.png 类的关系.png