public void addMessageObservers(final List<MessageObserver> observers){
  if (observers == null) {
    throw new NullPointerException();
  }
 else   if (messageObservers == null) {
    initMessageObserverList();
  }
  messageObservers.addAll(observers);
}

public void addMessageObservers ( final List < MessageObserver > observers ) { if ( observers == null ) { throw new NullPointerException ( ) ; } else if ( messageObservers == null ) { initMessageObserverList ( ) ; } messageObservers . addAll ( observers ) ; }
appends a list of observers to this message ' s existing observers .
