Thread Synchronization

      // File Name : Callme.java
     // This program uses a synchronized block.
     class Callme
     {
       void call(String msg)
       {
         System.out.print("[" + msg);
         try
         {
           Thread.sleep(1000);
         }
         catch (InterruptedException e)
         {
           System.out.println("Interrupted");
         }
         System.out.println("]");
       }
     }
     // File Name : Caller.java
     class Caller implements Runnable
     {
       String msg;
       Callme target;
       Thread t;
       public Caller(Callme targ, String s)
       {
         target = targ;
         msg = s;
         t = new Thread(this);
         t.start();
       }
       // synchronize calls to call()
       public void run()
       {
         synchronized(target)
         {
           // synchronized block
           target.call(msg);
         }
       }
     }
     // File Name : Synch.java
     class Synch
     {
       public static void main(String args[])
       {
         Callme target = new Callme();
         Caller ob1 = new Caller(target, "Hello");
         Caller ob2 = new Caller(target, "Synchronized");
         Caller ob3 = new Caller(target, "World");
        
         // wait for threads to end
         try
         {
           ob1.t.join();
           ob2.t.join();
           ob3.t.join();
         }
         catch(InterruptedException e)
         {
           System.out.println("Interrupted");
         }
       }
     }