class Anamial{

    public void eat(){
        System.out.println("动物吃");
    }
    
}

class Dog extends Anamial{
    public void eat(){
        System.out.println("狗吃骨头");
    }
    public void lookDoor(){
        System.out.println("狗看门");
    }
}

class Cat extends Anamial{
    public void eat(){
         System.out.println("猫吃鱼");
    }
    public void play(){
         System.out.println("狗玩游戏");
    }
    
}

class ExtendsDemo{
    public static void main(String[] args){
        System.out.println("Extends ");
        //定义动物为狗
        Anamial a = new Dog();
        a.eat();
        //a.lookDoor(); 编译会报错,动物没有狗的方法
        //将动物还原成狗
        Dog d = (Dog)a;
        d.eat();
        d.lookDoor();
        
        //a变成猫
        a = new Cat();
        a.eat();
        //a.play();  编译会报错,动物没有play方法
        
        //将动物还原为狗
        Cat c = (Cat)a;
        c.eat();
        c.play();
        
        //Dog dd = (Dog)a;  编译不会报错，运行报错 java.lang.ClassCastException: Cat cannot be cast to Dog
        //不能将毛转换成狗
        
        
    }
}