/**
   This program runs two threads in parallel.
*/
public class ThreadTester {
   public static void main(String[] args) {
      Runnable r1 = new GreetingProducer("Hello, World!");
      Runnable r2 = new GreetingProducer("Goodbye, World!");
      
      Thread t1 = new Thread(r1);
      Thread t2 = new Thread(r2);

      t1.start();
      t2.start();
   }
   
   boolean more_work_to_do = true;
   
   public void run() {
	   try {
		   while(more_work_to_do) {
			   // do work
			   Thread.sleep(DELAY);
		   }
	   } catch(InterruptedException e) {}
	   // clean up
   }
   
   long DELAY = 10;
}