State状态模式

   1. //先来一个状态：  
   2. package State;  
   3.   
   4. public abstract class State  
   5. {  
   6.       
   7.     /** *//** Creates a new instance of State */  
   8.     public State() {  
   9.     }  
  10.       
  11.     public abstract void opration(Context context);  
  12. }//end class State  
  13.   
  14. //在来两个具体的State：  
  15. public class ConcreteStateA extends State  
  16. {  
  17.       
  18.     /** *//** Creates a new instance of ConcreteStateA */  
  19.     public ConcreteStateA() {  
  20.     }  
  21.   
  22.     public void opration(Context context)  
  23.     {  
  24.         System.out.println("The Concrete A");  
  25.         context.setSate(new ConcreteStateB());  
  26.     }//end opration()  
  27.       
  28.     public static ConcreteStateA getInstance()  
  29.     {  
  30.         return new ConcreteStateA();  
  31.     }//end getInstance()  
  32. }  
  33.   
  34. public class ConcreteStateB extends State  
  35. {  
  36.       
  37.     /** *//** Creates a new instance of ConcreteStateB */  
  38.     public ConcreteStateB() {  
  39.     }  
  40.   
  41.     public void opration(Context context)  
  42.     {  
  43.         System.out.println("The Concrete B");  
  44.         context.setSate(new ConcreteStateA());  
  45.     }//end opration()  
  46.       
  47.     public static ConcreteStateB getInstance()  
  48.     {  
  49.         return new ConcreteStateB();  
  50.     }//end getInstance()  
  51.       
  52. }//end class ConcreteStateB  
  53.   
  54. //来一个场景：  
  55. public class Context  
  56. {  
  57.     private State state;  
  58.     /** *//** Creates a new instance of Context */  
  59.     public Context() {  
  60.     }  
  61.       
  62.     public void setSate(State stat)  
  63.     {  
  64.         state = stat;  
  65.     }//end setState()  
  66.       
  67.     public void operation()  
  68.     {  
  69.         state.opration(this);  
  70.     }//end operation()  
  71.       
  72. }//end class Context  
  73.   
  74. //怎样调用：  
  75. public static void main(String[] args)  
  76. {  
  77.         Context con = new Context();  
  78.         con.setSate(ConcreteStateA.getInstance());  
  79.         con.operation();  
  80.         con.operation();  
  81. }//end main()