It all sounds very exotic stuff, but if you want help here (which will probably focus on the Arduino side of things) you'll have to give some more information.
Which Arduino are you using ? There is quite a variety (including clones) which have a numer of specialities for talking to the host including USB.
On what platform are you running your Java environment ?
How is the Arduino connected to the platform running Java (diagram/schematic) ?
What code are you using on the Arduino (code listing here between code tags) ?
Are you following any tutorial to get this communication working (link) ?
okay i m using java net beans plateform, and i m using arduino gunuino uno, and circuit connection just simple LED to bread bord and to the arduinoand to my system com3 port,
here connection and coding are correct as i m sure of that but problem is while serial communicating with java net beans i m usinf RXTX comm driver to communicate but i dont understand why netbeans is not running base on what giv a file path to java..
i add jar file to my project library and and i give proper it java path and source,
so i went through all tutorial but its not working..
if anybody knows how to give proper RXTX file in netbeans..