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());

    }
 }