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*/

 1 import java.util.*;
 2 class Animalb{
 3     String name;
 4     void eat(){
 5         System.out.println("动物在吃东西啦");
 6     }
 7 }
 8 class Doga extends Animalb{}
 9 class Cata extends Animalb{}
10 
11 public class FourFei {
12    public static void main(String[] args){
13        Doga a = new Doga();
14        Cata c = new Cata();
15        
16        ArrayList<Object> list = new ArrayList<Object>();
17        list.add(a);
18        list.add(c);
19        
20        if(a.equals(c)){ //判断两个对象是否相等
21            System.out.println("true");
22        }else{
23            System.out.println("false");
24        }
25        System.out.println(c.equals(a));
26        System.out.println(c.getClass());
27        System.out.println(c.hashCode());
28        System.out.println(c.toString());
29        
30    }
31 }