// Fig. 16.3: ThreadTester.java
// Multiple threads printing at different intervals.

public class ThreadTester {

   public static void main( String [] args )
   {
      // create and name each thread
      PrintThread thread1 = new PrintThread( "thread1" );
      PrintThread thread2 = new PrintThread( "thread2" );
      PrintThread thread3 = new PrintThread( "thread3" );
        
      System.err.println( "Starting threads" );
        
      thread1.start(); // start thread1 and place it in ready state
      thread2.start(); // start thread2 and place it in ready state
      thread3.start(); // start thread3 and place it in ready state
        
      System.err.println( "Threads started, main ends\n" );
        
   } // end main
    
} // end class ThreadTester

// class PrintThread controls thread execution
class PrintThread extends Thread {
   private int sleepTime;
    
   // assign name to thread by calling superclass constructor
   public PrintThread( String name )
   {
      super( name );
        
      // pick random sleep time between 0 and 5 seconds
      sleepTime = ( int ) ( Math.random() * 5001 );
   }        
    
   // method run is the code to be executed by new thread
   public void run()
   {
      // put thread to sleep for sleepTime amount of time
      try {
         System.err.println( 
            getName() + " going to sleep for " + sleepTime );
            
         Thread.sleep( sleepTime );
      }
        
      // if thread interrupted during sleep, print stack trace
      catch ( InterruptedException exception ) {
         exception.printStackTrace();
      }
        
      // print thread name
      System.err.println( getName() + " done sleeping" );
    
   } // end method run
    
} // end class PrintThread



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