java USB标准

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 1 interface USB{
 2     public void start();
 3     public void stop();
 4 }
 5 class Computer{
 6     public static void plugin(USB usb){
 7         usb.start();
 8         System.out.println("=========USB device is working======");
 9         usb.stop();
10     }
11 };
12 class Flash implements USB{
13     public void start(){
14         System.out.println("U-disk starts working...");
15     }
16     public void stop(){
17         System.out.println("U-disk stops working...");
18     }
19 };
20 class Print implements USB{
21     public void start(){
22         System.out.println("Printer starts working...");
23     }
24     public void stop(){
25         System.out.println("Printer stops working...");
26     }
27 }
28 
29 public class InterfaceCaseDemo02 {
30     public static void main(String args[]){
31         Computer.plugin(new Flash());
32         Computer.plugin(new Print());
33     }
34 }

可以看出，计算机关心的只是接口，对于具体设备，毫不关心。