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，让他们之间可以互相替换，此模式让算法的变化独立于适用算法的客户。

 

注：首先我用的是Head First 设计模式这本书，里面的所有代码都放在了博主的GitHub里面，地址：https://github.com/Stray-Kite/Design-Pattern ，读者们可以自行下载哦。注：本次的代码在策略模式那个文档里，也就是strategy文档里面。

 

 

下面是这一节的最终代码：

 

首先让我们看一下这个项目的整体架构，图不是很清楚，但是应该还是能看的八九不离十，望读者见谅；有些功能没有写，但是在GitHub

里面有，读者可以自行下载研究哦，其实都是一些重复操作，哈哈：

 

Duck.java:

 1 package headfirst.designpatterns.strategy;
 2 
 3 public abstract class Duck {
 4     FlyBehavior flyBehavior;
 5     QuackBehavior quackBehavior;
 6 
 7     public Duck() {
 8     }
 9 
10     public void setFlyBehavior(FlyBehavior fb) {
11         flyBehavior = fb;
12     }
13 
14     public void setQuackBehavior(QuackBehavior qb) {
15         quackBehavior = qb;
16     }
17 
18     abstract void display();
19 
20     public void performFly() {
21         flyBehavior.fly();
22     }
23 
24     public void performQuack() {
25         quackBehavior.quack();
26     }
27 
28     public void swim() {
29         System.out.println("All ducks float, even decoys!");
30     }
31 }

 

输入并编译FlyBehavior接口（FlyBehavior.java）与三个行为实现类（FlyWithWings.java和FylNoWay.java和FlyRocketPowered.java）

FlyBehavior.java（管鸭子的飞行行为）:

1 package headfirst.designpatterns.strategy;
2 
3 public interface FlyBehavior {
4     public void fly();
5 }

FlyWithWings.java:

1 package headfirst.designpatterns.strategy;
2 
3 public class FlyWithWings implements FlyBehavior {
4     public void fly() {
5         System.out.println("I'm flying!!");
6     }
7 }

FlyNoWay.java:

1 package headfirst.designpatterns.strategy;
2 
3 public class FlyNoWay implements FlyBehavior {
4     public void fly() {
5         System.out.println("I can't fly");
6     }
7 }

FlyRocketPowered.java(火箭动力飞行):

1 package headfirst.designpatterns.strategy;
2 
3 public class FlyRocketPowered implements FlyBehavior {
4     public void fly() {
5         System.out.println("I'm flying with a rocket");
6     }
7 }

 

输入并编译QuackBehavior接口（QuackBehavior.java）与三个行为实现类（Quack.java和MuteQuack.java和Squeak.java）

QuackBehavior.java（管鸭子叫声行为）:

1 package headfirst.designpatterns.strategy;
2 
3 public interface QuackBehavior {
4     public void quack();
5 }

Quack.java:

1 package headfirst.designpatterns.strategy;
2 
3 public class Quack implements QuackBehavior {
4     public void quack() {
5         System.out.println("Quack");
6     }
7 }

MuteQuack.java:

1 package headfirst.designpatterns.strategy;
2 
3 public class MuteQuack implements QuackBehavior {
4     public void quack() {
5         System.out.println("<< Silence >>");
6     }
7 }

Squeak.java:

1 package headfirst.designpatterns.strategy;
2 
3 public class Squeak implements QuackBehavior {
4     public void quack() {
5         System.out.println("Squeak");
6     }
7 }

创建一个绿头鸭：

package headfirst.designpatterns.strategy;

public class MallardDuck extends Duck {

    public MallardDuck() {

        quackBehavior = new Quack();
        flyBehavior = new FlyWithWings();

    }

    public void display() {
        System.out.println("I'm a real Mallard duck");
    }
}

在创建一个模型鸭：

 1 package headfirst.designpatterns.strategy;
 2 
 3 public class ModelDuck extends Duck {
 4     public ModelDuck() {
 5         flyBehavior = new FlyNoWay();
 6         quackBehavior = new Quack();
 7     }
 8 
 9     public void display() {
10         System.out.println("I'm a model duck");
11     }
12 }

 

最后让我们来一个测试类（MiniDuckSimulator.java）：

 1 package headfirst.designpatterns.strategy;
 2 
 3 public class MiniDuckSimulator1 {
 4  
 5     public static void main(String[] args) {
 6  
 7         Duck mallard = new MallardDuck();
 8         mallard.performQuack();
 9         mallard.performFly();
10    
11         Duck model = new ModelDuck();
12         model.performFly();
13         model.setFlyBehavior(new FlyRocketPowered());
14         model.performFly();
15 
16     }
17 }

运行结果如下图所示：