private boolean messageChanged(String oldMessage,String newMessage){
  return ((newMessage == null) && (oldMessage != null)) || ((newMessage != null) && !newMessage.equals(oldMessage));
}

private boolean messageChanged ( String oldMessage , String newMessage ) { return ( ( newMessage == null ) && ( oldMessage != null ) ) || ( ( newMessage != null ) && ! newMessage . equals ( oldMessage ) ) ; }
check if a message string has changed .
