public void removeMessageObserver(final MessageObserver observer){
  if (observer == null) {
    throw new NullPointerException();
  }
 else   if (messageObservers != null) {
    messageObservers.remove(observer);
  }
}

public void removeMessageObserver ( final MessageObserver observer ) { if ( observer == null ) { throw new NullPointerException ( ) ; } else if ( messageObservers != null ) { messageObservers . remove ( observer ) ; } }
removes the specified message observer .
