JAVA设计模式之策略模式

策略模式：定义了算法族，分别封装起来，让它们之间可以互相替换，此模式让算法的变化独立于使用算法的客户。

例子：设计一个鸭子类，有的鸭子会飞但有的不会飞；有的鸭子会叫但有的不会叫；所有的鸭子都有一个不同的外观。

 1 public interface FlyBehavior
 2 {
 3     public void fly();
 4 }
 5 
 6 public class FlyWithWings implements FlyBehavior
 7 {
 8     public void fly() 
 9     {
10         System.out.println("I'm flying!");
11     }
12 }
13 
14 public class FlyNoWay implements FlyBehavior
15 {
16     public void fly() 
17     {
18         System.out.println("I can't fly!");
19     }
20 }
21 
22 public interface QuackBehavior 
23 {
24     public void quack();
25 }
26 
27 public class Quack implements QuackBehavior
28 {
29     public void quack() 
30     {
31         System.out.println("Quack!");
32     }
33 }
34 
35 public class MuteQuack implements QuackBehavior
36 {
37     public void quack() 
38     {
39         System.out.println("<Silence>");
40     }
41 }
42 
43 public abstract class Duck 
44 {
45     FlyBehavior flyBehavior;
46     QuackBehavior quackBehavior;
47     
48     public abstract void display();
49     
50     public void performFly()
51     {
52         flyBehavior.fly();
53     }
54     
55     public void performQuack()
56     {
57         quackBehavior.quack();
58     }
59 }
60 
61 public class MallardDuck extends Duck
62 {
63     public MallardDuck(FlyBehavior flyBehavior, QuackBehavior quackBehavior)
64     {
65         this.quackBehavior = quackBehavior;
66         this.flyBehavior = flyBehavior;
67     }
68 
69     @Override
70     public void display() 
71     {
72         System.out.println("I'm a real Mallard Duck!");
73     }
74 }
75 
76 public class test 
77 {
78     public static void main(String[] args)
79     {
80         Duck duck = new MallardDuck(new FlyWithWings(), new MuteQuack());
81         duck.performFly();
82         duck.performQuack();
83         duck.display();
84     }
85 }

参考：《headfirst设计模式》、http://yangguangfu.iteye.com/blog/815107