設計模式 - 裝飾者模式

1. 定義：動態的將責任附加到對象上。若要擴展功能，裝飾者提供了比繼承更有彈性的替代方案。

2. 類結構圖：

3. 代碼實現

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 飲料 抽象類
 5  * @author Administrator
 6  */
 7 
 8 public abstract class Beverage {
 9     
10     // 描述
11     String description = "Unknown Beverage";
12     
13     // 獲取飲料描述
14     public String getDescription(){
15         return this.description;
16     }
17     
18     // 計算價格方法
19     public abstract double cost();
20 
21 }

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 綜合 - 咖啡
 5  * @author Administrator
 6  *
 7  */
 8 
 9 public class HouseBlend extends Beverage {
10     
11     public HouseBlend(){
12         description = "House Blend Coffee";
13     }
14 
15     @Override
16     public double cost() {
17         return 0.89;
18     }
19 
20 }

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 深陪 - 咖啡
 5  * @author Administrator
 6  *
 7  */
 8 
 9 public class DarkRoast extends Beverage {
10     
11     public DarkRoast(){
12         description = "Dark Roast Coffee";
13     }
14 
15     @Override
16     public double cost() {
17         return 0.99;
18     }
19 
20 }

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 超濃縮 - 咖啡
 5  * @author Administrator
 6  */
 7 
 8 public class Espresso extends Beverage {
 9     
10     public Espresso(){
11         description = "Espresso Coffee";
12     }
13 
14     @Override
15     public double cost() {
16         return 1.99;
17     }
18 
19 }

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 濃縮 - 咖啡
 5  * @author Administrator
 6  *
 7  */
 8 
 9 public class Decat extends Beverage {
10     
11     public Decat(){
12         description = "Decat Coffee";
13     }
14 
15     @Override
16     public double cost() {
17         return 1.99;
18     }
19 
20 }

//-----------------------------------------------------------------------

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 調味品 - 裝飾者
 5  * @author Administrator
 6  *
 7  */
 8 
 9 public abstract class CondimentDecorator extends Beverage {
10     
11     // 所有的飲料裝飾著必須重新實現此方法
12     public abstract String getDescription();
13 
14 }

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 摩卡- 配料
 5  * @author Administrator
 6  *
 7  */
 8 
 9 public class Mocha extends CondimentDecorator {
10     
11     // 用一個實例變數記錄飲料，也就是被裝飾者
12     Beverage beverage;
13 
14     public Mocha(Beverage beverage){
15         this.beverage = beverage;
16     }
17     
18     @Override
19     public String getDescription() {
20         return beverage.getDescription() + ", Mocha";
21     }
22     
23     // 計算摩卡價格
24     public double cost(){
25         return 0.20 + beverage.cost();
26     }
27     
28 
29 }

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 豆漿 - 配料
 5  * @author Administrator
 6  *
 7  */
 8 
 9 public class Soy extends CondimentDecorator {
10     
11     // 記錄飲料被裝飾者
12     Beverage beverage;
13     
14     public Soy(Beverage beverage){
15         this.beverage = beverage;
16     }
17 
18     @Override
19     public String getDescription() {
20         return beverage.getDescription() + ", Soy";
21     }
22     
23     public double cost(){
24         return 0.15 + beverage.cost();
25     }
26 
27 }

 1 package com.dcz.decorate;
 2 
 3 /**
 4  * 奶泡 - 配料
 5  * @author Administrator
 6  *
 7  */
 8 
 9 public class Whip extends CondimentDecorator {
10     
11     Beverage beverage;
12     
13     public Whip(Beverage beverage){
14         this.beverage = beverage;
15     }
16 
17     @Override
18     public String getDescription() {
19         return beverage.getDescription() + ", Ship";
20     }
21     
22     // 計算奶泡價格
23     public double cost(){
24         return 0.10 + beverage.cost();
25     }
26 
27 }

// ----------------------------------------------------------------------------------------以下是測試類

 1 package com.dcz.decorate;
 2 
 3 public class TestStrbuzzCoffee {
 4     
 5     public static void main(String[] args) {
 6         
 7         // 要一杯超濃縮咖啡
 8         Beverage espresso = new Espresso();
 9         System.out.println(espresso.getDescription() + ", $:" + espresso.cost());
10         
11         // 要一杯深陪咖啡，雙倍摩卡加奶泡
12         Beverage darkRoast = new DarkRoast();
13         // 使用第一個摩卡裝飾
14         darkRoast = new Mocha(darkRoast);
15         // 使用第二個摩卡裝飾
16         darkRoast = new Mocha(darkRoast);
17         // 使用奶泡裝飾
18         darkRoast = new Whip(darkRoast);
19         System.out.println(darkRoast.getDescription() + ", $:" + darkRoast.cost());
20         
21         // 最後要在一杯調料為豆漿，摩卡，奶泡的綜合咖啡
22         Beverage HouseBlend = new HouseBlend();
23         // 使用豆漿裝飾
24         HouseBlend = new Soy(HouseBlend);
25         // 使用摩卡裝飾
26         HouseBlend = new Mocha(HouseBlend);
27         // 使用奶泡裝飾
28         HouseBlend = new Whip(HouseBlend);
29         System.out.println(HouseBlend.getDescription() + ", $:" + HouseBlend.cost());
30         
31     }
32 
33 }