【Java 基础篇】【第十课】多态

 1 public class ten
 2 {
 3     public static void main(String[] args)
 4     {
 5         Human guest = new Human();
 6         BrokenCup hisCup = new BrokenCup();
 7 
 8         // 虽然Human中的函数drink的参数一为Cup，
 9         // 但是多态的机制决定了它调用的是继承自Cup的BrokenCup
10         guest.drink(hisCup, 10);
11     }
12 
13 }
14 
15 class Human
16 {
17     void drink(Cup aCup, int w)
18     {
19         aCup.drinkWater(w);
20     }
21 }
22 
23 // 水杯
24 class Cup
25 {
26     private int water = 0;
27 
28     public void addWater(int w)
29     {
30         this.water = this.water + w;
31     }
32 
33     public void drinkWater(int w)
34     {
35         this.water = this.water - w;
36     }
37 }
38 
39 // 破杯子
40 class BrokenCup extends Cup
41 {
42     // 重写了父类的方法
43     public void addWater(int w)
44     {
45         System.out.println("shit, broken cup");
46     }
47 
48     public void drinkWater(int w)
49     {
50         System.out.println("oh, no water inside");
51     }
52 }

oh, no water inside