/**
 * Create 8 child threads, let them sleep,
 *   then monitor when they terminate
 */
public class Octuplets
{
 // This is the thread code itself
 class Child extends Thread
 {
   public void run() {
     int t = 10 + (int)( Math.random() * 21 );  // 10-30 seconds
     System.out.println( "THREAD: I'm new. I'm gonna nap for " + t +
                         " seconds." );
     try {
       Thread.sleep( t * 1000 );  // milliseconds
     }
     catch( InterruptedException ex ) {  /* ... */  }
   }
 }

 // This is the main thread
 public void manageThreads()
 {
   int children = 8;
   Thread[] threads = new Thread[ children ];

   // Create the Thread objects
   for ( int i = 0 ; i < children ; i++ ) {
     threads[i] = new Thread( new Child() );
   }

   // START the threads
   for ( int i = 0 ; i < children ; i++ ) {
     threads[i].start();
   }

   System.out.println( "MAIN THREAD: I'm waiting for my children." );

   int n = children;

   while ( n > 0 )
   {
     for ( int i = 0 ; i < children ; i++ )
     {
       if ( threads[i] != null  &&  threads[i].isAlive() == false )
       {
         /* detected a thread that has completed its execution */

         try {
           threads[i].join();
         }
         catch( InterruptedException ex )  {  /* ... */  }

         System.out.println( "MAIN THREAD: caught a thread." );
         threads[i] = null;
         n--;
         System.out.println( "MAIN THREAD: " + n + " more to go..." );
       }
     }
   }
 }



 public static void main( String[] args )
 {
   Octuplets object = new Octuplets();
   object.manageThreads();
 }

}