一、策略模式介绍

二、策略模式引入

需求：

UML类图：

代码实现(Java):

public interface FlyBehavior {

    void fly(); // 子类具体实现
}

public class NoFlyBehavior implements FlyBehavior{

    @Override
    public void fly() {
        System.out.println(" 不会飞翔  ");
    }

}

public class BadFlyBehavior implements FlyBehavior {

    @Override
    public void fly() {
        System.out.println(" 飞翔技术一般 ");
    }

}

public class GoodFlyBehavior implements FlyBehavior {

    @Override
    public void fly() {
        System.out.println(" 飞翔技术高超 ~~~");
    }

}

public interface QuackBehavior {
    void quack();//子类实现
}

public abstract class Duck {

    //属性, 策略接口
    FlyBehavior flyBehavior;
    //其它属性<->策略接口
    QuackBehavior quackBehavior;

    public Duck() {

    }

    public abstract void display();//显示鸭子信息

    public void quack() {
        System.out.println("鸭子嘎嘎叫~~");
    }

    public void swim() {
        System.out.println("鸭子会游泳~~");
    }

    public void fly() {

        //改进
        if(flyBehavior != null) {
            flyBehavior.fly();
        }
    }

    public void setFlyBehavior(FlyBehavior flyBehavior) {
        this.flyBehavior = flyBehavior;
    }


    public void setQuackBehavior(QuackBehavior quackBehavior) {
        this.quackBehavior = quackBehavior;
    }

}

public class PekingDuck extends Duck {

    //假如北京鸭可以飞翔，但是飞翔技术一般
    public PekingDuck() {
        flyBehavior = new BadFlyBehavior();

    }

    @Override
    public void display() {
        System.out.println("~~北京鸭~~~");
    }

}

public class WildDuck extends Duck {

    //构造器，传入FlyBehavor 的对象
    public  WildDuck() {
        flyBehavior = new GoodFlyBehavior();
    }

    @Override
    public void display() {
        System.out.println(" 这是野鸭 ");
    }

}

public class ToyDuck extends Duck{

    public ToyDuck() {
        flyBehavior = new NoFlyBehavior();
    }

    @Override
    public void display() {
        System.out.println("玩具鸭");
    }

    //需要重写父类的所有方法

    public void quack() {
        System.out.println("玩具鸭不能叫~~");
    }

    public void swim() {
        System.out.println("玩具鸭不会游泳~~");
    }

}

public class Client {

    public static void main(String[] args) {
        WildDuck wildDuck = new WildDuck();
        wildDuck.fly();//

        ToyDuck toyDuck = new ToyDuck();
        toyDuck.fly();

        PekingDuck pekingDuck = new PekingDuck();
        pekingDuck.fly();

        //动态改变某个对象的行为, 北京鸭 不能飞
        pekingDuck.setFlyBehavior(new NoFlyBehavior());
        System.out.println("北京鸭的实际飞翔能力");
        pekingDuck.fly();
    }

}

三、策略模式在JDK-Arrays应用的源码分析

四、策略模式注意事项和细节