多种设计模式备忘

public class ApplicationRunner { 
           private Application itsApplication = null; 
           public ApplicationRunner(Application app) 
          {
                   itsApplication = app; 
          } 
          public void run()
         {
                   itsApplication.init(); 
                   itsApplication .idle(); 
                   itsApplication.cleanup(); 
         } 
} 


public interface Application { 
         public void init(); 
         public void idle(); 
         public void cleanup(); 
} 


public class ftocStrat implements Application { 

//实现Application 
new ApplicationRunner实例 
} 

 1、单例模式 SINGLETON

Singleton类的实例不会超过一个。

实现：

public class Singleton {
        private static Singleton theInstance = null; 
        private Singleton(){} 
        public static Singleton Instance() {
            if(theInstance == null)
            theInstance = new Singleton();
        return theInstance; 
        } 
} 

2、MONOSTATE模式

实现：

Public class Monostate { 
         private static int itsX = 0;
         public Monostate(){} 
         public void set(int x) { 
         itsX=x; 
         } 
         public int getX() 
         { return itsX; } 
} 

3、NULL OBJECT模式

该模式通常会消除对null进行检查的需要，并且有助于代码简化。

实现：

public interface Employee { 
         public boolean isTimeToPlay(Date payDate); 
         public void pay();
         public static final Employee NULL = new Employee() 
        { 
              public boolean isTimeToPay(Date payDate) 
             { 
                   return false; 
             }
             public void pay() 
            { 
             }
         } 
}


 if(e == Employee.NULL) 

 
4、模板方法模式

实现：

public abstract class Application { 
       private boolean isDone = false; 
       protected abstractca void init(); 
       protected abstractca void idle(); 
       protected abstractca void cleanup(); 
       protected void setDone() 
      {
          isDone = true;
      } 
       protected boolean done() 
       {
            return isDone;
       } 
       public void run() 
      {
            init(); 
            idle(); 
            cleanup(); 
       } 
} //子类实现 

 
5、策略模式

public class ApplicationRunner 
{
         private Application itsApplication = null; 
         public ApplicationRunner(Application app) 
         {
                itsApplication = app; 
         } 
         public void run() 
         {
                 itsApplication.init(); 
                 itsApplication .idle(); 
                 itsApplication.cleanup(); 
         } 
} 


public interface Application { 
           public void init(); 
           public void idle(); 
           public void cleanup(); 
} 


public class ftocStrat implements Application { 
//实现Application 
new ApplicationRunner实例 
}