设计模式-策略模式

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

UML图示：

 

代码示例：

/**封装飞的行为*/

public interface FlyBehavior {

    public void fly();

}

public class FlyNoWings implements FlyBehavior{

    @Override

    public void fly() {

        // TODO Auto-generated method stub

        System.out.println("fly not wings!");

    }

}

public class FlyNoWings implements FlyBehavior{

    @Override

    public void fly() {

        // TODO Auto-generated method stub

        System.out.println("fly not wings!");

    }

}

 

/**封装叫的行为*/

public interface QuackBehavior {

    public void quack();

}

public class Quack implements QuackBehavior{

    @Override

    public void quack() {

        // TODO Auto-generated method stub

        System.out.println("quack...");

    }

}

public class Squeak implements QuackBehavior{

    @Override

    public void quack() {

        // TODO Auto-generated method stub

        System.out.println("squeak...");

    }

}

 

/**使用封装好的算法族*/

public abstract class Duck {

    private FlyBehavior mFlyBehavior = null;

    private QuackBehavior mQuackBehavior = null;

    public void fly(){

        if(mFlyBehavior != null)

            mFlyBehavior.fly();

    }

    public void quack(){

        if(mQuackBehavior != null){

            mQuackBehavior.quack();

        }

    }

    public abstract void display();

    public void setQuackBehavior(QuackBehavior quack){

        mQuackBehavior = quack;

    }

    public void setFlyBehavior(FlyBehavior fly){

        mFlyBehavior = fly;

    }

}

 

public class RubberDuck extends Duck{

    public RubberDuck() {

        // TODO Auto-generated constructor stub

        setFlyBehavior(new FlyNoWings());

        setQuackBehavior(new Squeak());

    }

    @Override

    public void display() {

        // TODO Auto-generated method stub

        System.out.println("display rubber duck");

    }

}

public class RedHeadDuck extends Duck{

    public RedHeadDuck() {

        // TODO Auto-generated constructor stub

        setFlyBehavior(new FlyWithWings());

        setQuackBehavior(new Quack());

    }

    @Override

    public void display() {

        // TODO Auto-generated method stub

        System.out.println("display red head duck");

    }

}

 

public class Main {

    public static void main(String[] args) {

        Duck redHeadDuck = new RedHeadDuck();

        Duck rubberDuck = new RubberDuck();

        redHeadDuck.fly();

        redHeadDuck.quack();

        redHeadDuck.display();

        rubberDuck.fly();

        rubberDuck.quack();

        rubberDuck.display();

    }

}

 

测试结果：

fly with wring!

quack...

display red head duck

fly not wings!

squeak...

display rubber duck