CS 342 - 5/1/14

Singleton Pattern

class MyS
{
 private volatile static MyS x = null;

 private Object data;

 private MyS ()
  {
    // do initialization as needed
    data = new Object();
  }

 public static MyS getInstance()
  {
    if (x == null)
      {
        synchronized (MyS.class)
           {
             if (x == null)
                 x = new MyS();
           }
      }

    return x;
  }

 public Object getData()
   {
        return data;
   }

 public void setData (Object d)
   {
     data = d;
   }

 public .... other methods ...

}


methodZ
{
  MyS s1 = MyS.getInstance();

  z = s1.getData();
}

methodY
{
   MyS s2 = MyS.getInstance();

   y = s2.getData();
}
 

---------------------
Threads
   start()
   run()

   Create an instance of the Thread() of something
     that inherits from Thread()

   class MyThread extends Thread()
     {
       static int shared;
       Object s;
       int value; 
       public MyThread (int v, Object o)
         {
          value = v;
          s = o;
          //start();
         }
       public void run()
         {
          System.out.println ("New Thread with value: "
                + value );
          ....
           if (...)
              return;
          .....
         }
      }

     // in  some other method
    Object o = new Object();


    MyThread x1 = new MyThread(5, o);
    MyThread x2 = new MyThread(7, o);
    x1.start();
    System.out.println ("Original Thread");

--------------
Sockets  focus on connection section

Server side                         Client side
-------------                       -------------
create ServerSocket instance
accept() method on ServerSocket
                                   
                                    create Socket instance
                                       using machine info
                                       and port info of the
                                       serverSocket

accept() method returns with
  an instance of socket for the
  server side to use

use socket instance to commincation  use socket instance to
  with client                           comminucate with server


-----
Multiple simultaneous clients to the same server

The accept() code nededs to be put in a loop that
  spawns a new thread for each client connection.
  The threads must be given the Socket instance that
  was returned by accept()