1 abstract class Animal
2 {
3 abstract void eat();
4 }
5
6 class Cat extends Animal
7 {
8 void eat()
9 {
10 System.out.println("eat fish");
11 }
12 }
13
14 class Dog extends Animal
15 {
16 void eat()
17 {
18 System.out.println("gnaw bone");
19 }
20 }
21
22 class Pig extends Animal
23 {
24 void eat()
25 {
26 System.out.println("eat rice");
27 }
28 }
29
30 class Duotai
31 {
32 public static void main(String[] args)
33 {
34 method(new Cat());
35 method(new Dog());
36 method(new Pig());
37 }
38 public static void method(Animal a)
39 {
40 a.eat();
41 }
42 }