非Animal呢？为何不写个万用类

/*4.非Animal呢？为何不写个万用类
 * 类Object是JAVA里多有类的源头/父类*/

import java.util.*;
class Animalb{
    String name;
    void eat(){
        System.out.println("动物在吃东西啦");
    }
}
class Doga extends Animalb{}
class Cata extends Animalb{}

public class FourFei {
   public static void main(String[] args){
       Doga a = new Doga();
       Cata c = new Cata();
       
       ArrayList<Object> list = new ArrayList<Object>();
       list.add(a);
       list.add(c);
       
       if(a.equals(c)){ //判断两个对象是否相等
           System.out.println("true");
       }else{
           System.out.println("false");
       }
       System.out.println(c.equals(a));
       System.out.println(c.getClass());
       System.out.println(c.hashCode());
       System.out.println(c.toString());
       
   }
}