code: private static String getNotificationID() {
          NotificationManager.ID_COUNTER = NotificationManager.ID_COUNTER+1;
          logger.fine("Notifications identifier counter: "+ID_COUNTER);
          return "Notification#" + (NotificationManager.ID_COUNTER);
      }
docs: Each new notification needs a notification-ID. NotificationManager monitors the number of
  notifications and generates a unique identifier for each of them, using this method to obtain it.
  
  @return
  a notification ID corresponding with the number of notifications saved on this simulation.