Java学习之多态

 1 /*
 2 需求：电脑运行实例，
 3 电脑运行基于主板。主板中可以有网卡、显卡、声卡等插件
 4 */
 5 
 6 //主板统一接口
 7 interface PCI
 8 {
 9     public void open();
10     public void close();
11 }
12 
13 //主板类
14 class MainBoard
15 {
16     public void run()
17     {
18         System.out.println("mainboard run ");
19     }
20     public void usePCI(PCI p)//PCI p = new NetCard()//接口型引用指向自己的子类对象。
21     {
22         if(p!=null)
23         {
24             p.open();
25             p.close();
26         }
27     }
28 }
29 
30 //网卡类
31 class NetCard implements PCI
32 {
33     public void open()
34     {
35         System.out.println("netcard open");
36     }
37     public void close()
38     {
39         System.out.println("netcard close");
40         method();
41     }
42 }
43 
44 //声卡类
45 class SoundCard implements PCI
46 {
47     public void open()
48     {
49         System.out.println("SoundCard open");
50     }
51     public void close()
52     {
53         System.out.println("SoundCard close");
54     }
55 }
56 
57 class DuoTaiDemo 
58 {
59     public static void main(String[] args) 
60     {
61         MainBoard mb = new MainBoard();
62         mb.run();
63         mb.usePCI(null);
64         mb.usePCI(new NetCard());
65         mb.usePCI(new SoundCard());
66     }
67 }