多态的使用

 1 abstract class Animala{
 2     String name;
 3     abstract public void eat();
 4
 5 }
 6 class Dog extends Animala{
 7     public void eat(){
 8         System.out.println("狗吃骨头");
 9     }
10 }
11 class Cat extends Animala{
12     public void eat(){
13         System.out.println("猫吃鱼");
14     }
15 }
16 class MyAnimalList{
17     private Animala[] animals = new Animala[5]; //初始化数组，即这个数组里可以放5个Animala类型的类的对象
18     private int nextIndex = 0; //下标
19
20     public void add(Animala a){
21         if(nextIndex < animals.length){
22             animals[nextIndex] = a;
23             System.out.println("Animal add at "+ nextIndex );
24             nextIndex++;
25         }
26     }
27 }
28 public class ThreeDuo {
29     public static void main(String[] args){
30         MyAnimalList list = new MyAnimalList(); //定义集合的对象
31         Cat a = new Cat();
32         Dog c = new Dog();
33         list.add(a);
34         list.add(c);
35     }
36 }