二十三种设计模式(第二十二种)-----策略模式(Strategy)

尚硅谷视频连接https://www.bilibili.com/video/BV1G4411c7N4?from=search&seid=11487053970269878470

类图

从上图可以看到，客户context有成员变量strategy或者其他的策略接口，至于需要使用到那个策略，我们可以在构造器中指定

需求

有各种鸭子(如：野鸭、北京鸭、水鸭等，鸭子有各种行为，比如叫、飞行等待)

显示鸭子的信息

需求类图

代码

1.鸭子抽象类

public abstract class Duck {    //策略接口    protected FlyBehavior flyBehavior;    public abstract void display();    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() {        if (flyBehavior != null) {            flyBehavior.fly();        }    }    public void setFlyBehavior(FlyBehavior flyBehavior) {        this.flyBehavior = flyBehavior;    }}

2.鸭子飞接口

public interface FlyBehavior {    void fly();}

3.不同鸭子实现类

public class WildDuck extends Duck {    public WildDuck() {        flyBehavior = new GoodFlyBehavior();    }    @Override    public void display() {        System.out.println("这是野鸭....");    }}//================================public class PekingDuck extends Duck {    public PekingDuck() {        flyBehavior = new BadFlyBehavior();    }    @Override    public void display() {        System.out.println("这是北京鸭子...");    }}//================================public class ToyDuck extends Duck {    public ToyDuck() {        flyBehavior = new NoFlyBehavior();    }    @Override    public void display() {        System.out.println("这是玩具鸭...");    }    @Override    public void quack() {        System.out.println("玩具鸭不能叫...");    }    @Override    public void swim() {        System.out.println("玩具鸭不能游泳...");    }}

4.不同飞实现类

public class GoodFlyBehavior implements FlyBehavior {    @Override    public void fly() {        System.out.println("飞翔技术高超...");    }}//================================public class BadFlyBehavior implements FlyBehavior {    @Override    public void fly() {        System.out.println("飞翔技术一般...");    }}//================================public class NoFlyBehavior implements FlyBehavior {    @Override    public void fly() {        System.out.println("不会飞...");    }}

5.客户端

public class Strategy {    public static void main(String[] args) {        WildDuck wildDuck = new WildDuck();        wildDuck.fly();        PekingDuck pekingDuck = new PekingDuck();        pekingDuck.fly();        ToyDuck toyDuck = new ToyDuck();        toyDuck.fly();        //更改pekingDuck飞行行为        pekingDuck.setFlyBehavior(new NoFlyBehavior());        pekingDuck.fly();    }}