策略模式：（分別封裝行為接口，實現算法族，超類裏放行為接口對象，在子類裏具體設定行為對象）

原則：

　　分離變化部分，封裝接口，基於接口編程各種功能。此模式讓行為算法的變化獨立於算法的使用者。

舉例說明：

　　分別封裝行為接口：FlyBehavior、QuackBehavior；

　　實現算法族：BadFlyBehavior、GoodFlyBehavior、NoFlyBehavior；GaGaQuackBehavior、GeGeQuackBehavior、NoQuackBehavior；

　　超類裏放行為接口對象：

　　在子類裏具體設定行為對象：

　　在使用的時候：

例子結構：

1 package com.java.hexter.stimulateduck.flybehavior;
2 
3 public interface FlyBehavior {
4     void fly();
5 }

1 package com.java.hexter.stimulateduck.quackbehavior;
2 
3 public interface QuackBehavior {
4     void quack();
5 };

 1 package com.java.hexter.stimulateduck.duck;
 
 2 
 3 import com.java.hexter.stimulateduck.flybehavior.FlyBehavior;
 4 import com.java.hexter.stimulateduck.quackbehavior.QuackBehavior;
 5 
 6 public abstract class Duck {
 7 
 8     FlyBehavior mFlyBehavior;
 9     QuackBehavior mQuackBehavior;
10 
11     public Duck() {
12 
13     }
14 
15     public
 
 void Fly() {
16         mFlyBehavior.fly();
17     }
18 
19     public void Quack() {
20         mQuackBehavior.quack();
21     }
22 
23     public abstract void display();
24 
25     //為了增加代碼的靈活性，可以自己設定鴨子叫的方式
26     public void SetQuackBehavoir(QuackBehavior qb) {
27         mQuackBehavior = qb;
28     }
29     public void SetFlyBehavoir(FlyBehavior fb) {
30         mFlyBehavior = fb;
31     }
32 
33     public void swim() {
34         System.out.println("~~im swim~~");
35     }
36 }

 1 package com.java.hexter.stimulateduck.flybehavior;
 2 
 3 
 4 
 5 public class    BadFlyBehavior implements FlyBehavior
 6 {
 7     @Override
 8     public void fly() {
 9         // TODO Auto-generated method stub
10         System.out.println("--BadFly--");
11     }
12 }

 1 package com.java.hexter.stimulateduck.flybehavior;
 2 
 3 
 4 public class    GoodFlyBehavior implements FlyBehavior
 5 {
 6 
 7     @Override
 8     public void fly() {
 9         // TODO Auto-generated method stub
10         System.out.println("--GoodFly--");
11     }
12     
13 }

 1 package com.java.hexter.stimulateduck.flybehavior;
 2 
 3 
 4 public class    NoFlyBehavior implements FlyBehavior
 5 {
 6     @Override
 7     public void fly() {
 8         // TODO Auto-generated method stub
 9         System.out.println("--NoFly--");
10     }
11 }

 1 package com.java.hexter.stimulateduck.quackbehavior;
 2 
 3 
 4 public    class GaGaQuackBehavior implements QuackBehavior
 5 {
 6 
 7     @Override
 8     public void quack() {
 9         // TODO Auto-generated method stub
10         System.out.println("__GaGa__");
11     }
12     
13 }

 1 package com.java.hexter.stimulateduck.quackbehavior;
 2 
 3 
 4 public    class GeGeQuackBehavior implements QuackBehavior
 5 {
 6 
 7     @Override
 8     public void quack() {
 9         // TODO Auto-generated method stub
10         System.out.println("__GeGe__");
11     }
12     
13 }

 1 package com.java.hexter.stimulateduck.quackbehavior;
 2 
 3 
 4 public    class NoQuackBehavior implements QuackBehavior
 5 {
 6 
 7     @Override
 8     public void quack() {
 9         // TODO Auto-generated method stub
10         System.out.println("__NoQuack__");
11     }
12     
13 }

 1 package com.java.hexter.stimulateduck.duck;
 2 
 3 import com.java.hexter.stimulateduck.flybehavior.GoodFlyBehavior;
 4 import com.java.hexter.stimulateduck.quackbehavior.GaGaQuackBehavior;
 5 
 6 public class GreenHeadDuck extends Duck {
 7 
 8     public GreenHeadDuck() {
 9         mFlyBehavior = new GoodFlyBehavior();
10         mQuackBehavior = new GaGaQuackBehavior();
11     }
12 
13     @Override
14     public void display() {
15         // TODO Auto-generated method stub
16         System.out.println("**GreenHead**");
17     }
18 
19 }

 1 package com.java.hexter.stimulateduck.duck;
 2 
 3 import com.java.hexter.stimulateduck.flybehavior.BadFlyBehavior;
 4 
 5 import com.java.hexter.stimulateduck.quackbehavior.GeGeQuackBehavior;
 6 
 7 public class RedHeadDuck extends Duck {
 8 
 9     public RedHeadDuck() {
10         mFlyBehavior = new BadFlyBehavior();
11         mQuackBehavior = new GeGeQuackBehavior();
12     }
13 
14     @Override
15     public void display() {
16         // TODO Auto-generated method stub
17         System.out.println("**RedHead**");
18     }
19 
20 }

 1 package com.java.hexter.stimulateduck;
 2 
 3 import com.java.hexter.stimulateduck.duck.Duck;
 4 import com.java.hexter.stimulateduck.duck.GreenHeadDuck;
 5 import com.java.hexter.stimulateduck.duck.RedHeadDuck;
 6 import com.java.hexter.stimulateduck.flybehavior.NoFlyBehavior;
 7 import com.java.hexter.stimulateduck.quackbehavior.NoQuackBehavior;
 8 
 9 
10 public class StimulateDuck {
11 
12     public static void main(String[] args) {
13 
14         Duck mGreenHeadDuck = new GreenHeadDuck();
15         Duck mRedHeadDuck = new RedHeadDuck();
16 
17         mGreenHeadDuck.display();
18         mGreenHeadDuck.Fly();
19         mGreenHeadDuck.Quack();
20         mGreenHeadDuck.swim();
21 
22         mRedHeadDuck.display();
23         mRedHeadDuck.Fly();
24         mRedHeadDuck.Quack();
25         mRedHeadDuck.swim();
26         mRedHeadDuck.display();
27         mRedHeadDuck.SetFlyBehavoir(new NoFlyBehavior());
28         mRedHeadDuck.Fly();
29         mRedHeadDuck.SetQuackBehavoir(new NoQuackBehavior());
30         mRedHeadDuck.Quack();
31     }
32 
33 }

輸出結果：

**GreenHead**
--GoodFly--
__GaGa__
~~im swim~~
**RedHead**
--BadFly--
__GeGe__
~~im swim~~
**RedHead**
--NoFly--
__NoQuack__

例子該種方式實現的好處：新增行為簡單，行為類更好的復用，組合更方便。既有繼承帶來的復用好處，沒有挖坑

註意：

　　1.認真分析策略中變化部分與不變部分；

　　2.多用組合，少用繼承；用行為類組合，而不是行為的繼承；這樣做更有彈性。

23種設計模式之二（策略模式）