Java Object-Oriented USB Interface Example

1. Requirements:
　　1. Set up a USB interface on the computer.
　　2. When the computer is running, connect the mouse to the interface, and the mouse can use its own functions.
　　3. When the computer is running, connect the keyboard to the interface, and the keyboard can use its own functions.
(The role of using the interface: reduce the coupling between peripheral devices such as mouse and keyboard and the notebook computer. It can also increase the expandability of the computer.)

2. Example code:

  1  // Design, define USB interface rules 
  2  interface USB
   3  {
   4      /** 
  5      Run device
   6      */ 
  7      public  void open();
   8  }
   9  
10  // Describe computer 
11  class computer
 12  {
 13      /** 
14      computer run
 15      */ 
16      public  void run()
 17      {
 18          System.out.println("computer ......" );
 19      }
 20     
21      /** 
22      Use a peripheral device that conforms to the rules
 23      */ 
24      public  void useUSB(USB usb) // Define a reference to an interface type. 
25      {
 26          if (usb != null );
 27          {
 28              usb.open();
 29          }
 30      }
 31  }
 32  
33  class Mouse
 34  {
 35      public  void run()
 36      {
 37          System.out.println("Mouse . ....." );
 38     }
 39  }
 40  
41  class Keyboard
 42  {
 43      public  void run()
 44      {
 45          System.out.println("Keyboard ......" );
 46      }
 47  }
 48  
49  /** 
50  A compatible USB interface is connected mouse.
51  */ 
52  class MouseUSB extends Mouse implements USB
 53  {
 54      public  void open()
 55      {
 56         System.out.println("Mouse USB open ......" );
 57      }
 58  }
 59  
60  /** 
61  A USB-compliant keyboard is connected.
62  */ 
63  class KeyboardUSB extends Keyboard implements USB
 64  {
 65      public  void open()
 66      {
 67          System.out.println("Keyboard USB open ..." );
 68      }
 69  }
 70  
71  /** 
72  Something that conforms to the USB interface is connected.
73  */ 
74 class ThingUSB implements USB
 75  {
 76      public  void open()
 77      {
 78          System.out.println("open ..." );
 79      }
 80  }
 81  
82  class USBTest
 83  {
 84      public  static  void main(String[ ] arge)
 85      {
 86          /** 
87          computer c starts running
 88          */ 
89          computer c = new computer();
 90         c.run();
 91          
92          /** 
93          Connect the mouse m to the interface useUSB, the mouse can use its own functions
 94          */ 
95          MouseUSB m = new MouseUSB();
 96          c.useUSB(m);
 97          m. run();    
 98          
99          /** 
100          Connect the keyboard k to the interface useUSB, the keyboard can use its own functions
 101          */ 
102          KeyboardUSB k = new KeyboardUSB();
 103          c.useUSB(k);
 104          k.run( );
 105          
106          /** 
107          something connected to the interface useUSB, can use
 108          */ 
109         USB t = new ThingUSB(); // Polymorphism. Can be connected to the interface can be used. 
110          c.useUSB(t);
 111      }
 112 }

Third, the code runs: