29. Object class methods for inter-thread communication

• 
      wait()
      notify()
      notifyAll()
  
  

• Code that waits on a condition:

  
      // if there are no orders ready, wait
      while ( orderQueue.count() == 0 )
      {
          try
          {
              wait();
          }
          catch ( InterruptedException e )
          {
          }
      }
  
  

• Another thread satisfies the condition and notifies other threads:

  
      // add an order to the queue
      orderQueue.add( order ); 
  
      // notify other threads
      notifyAll();