策略模式：

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public abstract class Duck {
    FlyBehavior flyBehavior;
    QuackBehavior quackBehavior;

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

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

    public abstract void display();

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

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

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

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public interface FlyBehavior {
    public void fly();
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public interface QuackBehavior {
    public void quack();
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public
 
 class FlyNoWay implements FlyBehavior {

    public void fly() {
        System.out.println("no way fly~~~");
    }
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public class FlyWithWings implements FlyBehavior {

    public void fly() {
        System.out.println("fly~~~");
    }
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public class Quack implements QuackBehavior {

    public void quack() {
        System.out.println("gua gua ~~~");
    }
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public class Squeak implements QuackBehavior {

    public void quack() {
        System.out.println("zhi zhi ~~~");
    }
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public class FlyRocketPowered implements FlyBehavior {

    public void fly() {
        System.out.println("flying with rocket");
    }
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public class MallardDuck extends Duck {
    public MallardDuck() {
        quackBehavior = new Quack();
        flyBehavior = new FlyWithWings();
    }

    public void display() {
        System.out.println("real mallard duck.");
    }
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

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

    @Override
    public void display() {
        System.out.println("model duck");
    }
}

package com.zoey.allTest.pattern.headFirst.strategyPattern.book;

public class MiniDuckSimulator {

    public static void main(String[] args) {
        Duck ma = new MallardDuck();
        ma.performFly();
        ma.performQuack();

        System.out.println("------------------");
        Duck model = new ModelDuck();
        model.performFly();
        model.setFlyBehavior(new FlyRocketPowered());
        model.performFly();

    }

}