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:

package headfirst.designpatterns.strategy;

public abstract class Duck {
    FlyBehavior flyBehavior;
    QuackBehavior quackBehavior;

    public Duck() {
    }

    public void setFlyBehavior(FlyBehavior fb) {
        flyBehavior = fb;
    }

    public void setQuackBehavior(QuackBehavior qb) {
        quackBehavior = qb;
    }

    abstract void display();

    public void performFly() {
        flyBehavior.fly();
    }

    public void performQuack() {
        quackBehavior.quack();
    }

    public void swim() {
        System.out.println("All ducks float, even decoys!");
    }
}

 

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）:

package headfirst.designpatterns.strategy;

public interface FlyBehavior {
    public void fly();
}

FlyWithWings.java:

package headfirst.designpatterns.strategy;

public class FlyWithWings implements FlyBehavior {
    public void fly() {
        System.out.println("I'm flying!!");
    }
}

FlyNoWay.java:

package headfirst.designpatterns.strategy;

public class FlyNoWay implements FlyBehavior {
    public void fly() {
        System.out.println("I can't fly");
    }
}

FlyRocketPowered.java(火箭动力飞行):

package headfirst.designpatterns.strategy;

public class FlyRocketPowered implements FlyBehavior {
    public void fly() {
        System.out.println("I'm flying with a rocket");
    }
}

 

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）:

package headfirst.designpatterns.strategy;

public interface QuackBehavior {
    public void quack();
}

Quack.java:

package headfirst.designpatterns.strategy;

public class Quack implements QuackBehavior {
    public void quack() {
        System.out.println("Quack");
    }
}

MuteQuack.java:

package headfirst.designpatterns.strategy;

public class MuteQuack implements QuackBehavior {
    public void quack() {
        System.out.println("<< Silence >>");
    }
}

Squeak.java:

package headfirst.designpatterns.strategy;

public class Squeak implements QuackBehavior {
    public void quack() {
        System.out.println("Squeak");
    }
}

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：

package headfirst.designpatterns.strategy;

public class ModelDuck extends Duck {
    public ModelDuck() {
        flyBehavior = new FlyNoWay();
        quackBehavior = new Quack();
    }

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

 

最后让我们来一个测试类（MiniDuckSimulator.java）：

package headfirst.designpatterns.strategy;

public class MiniDuckSimulator1 {
 
    public static void main(String[] args) {
 
        Duck mallard = new MallardDuck();
        mallard.performQuack();
        mallard.performFly();
   
        Duck model = new ModelDuck();
        model.performFly();
        model.setFlyBehavior(new FlyRocketPowered());
        model.performFly();

    }
}

运行结果如下图所示：