public class Demo {

    public static void main(String[] args){

        Master ma = new Master();

        ma.feed(new Animal(), new Food());

        ma.feed(new Cat(), new Bone());

        ma.feed(new Dog(), new Fish());

    }

}

class Animal{

    public void eat(Food f){

        System.out.println("我是一个小动物，正在吃" + f.getFood());

    }

}

class Cat extends Animal{

    public void eat(Food f){

        System.out.println("我是一只小猫咪，正在吃" + f.getFood());

    }

}

class Dog extends Animal{

    public void eat(Food f){

        System.out.println("我是一只狗狗，正在吃" + f.getFood());

    }

}

class Food{

    public String getFood(){

        return "事物";

    }

}

class Fish extends Food{

    public String getFood(){

        return "鱼";

    }

}

class Bone extends Food{

    public String getFood(){

        return "骨头";

    }

}

class Master{

    public void feed(Animal an, Food f){

        an.eat(f);

    }

}