well, vishal, sorry for such a late reply.. im really busy now a days... but since you ask...
on the filesystem, u can , IF YOU KNOW WHAT YOU ARE DOING perhaps try changin the .jad and .jar files to see wheather custom java MIDLets can be uploaded to the phone...
But whatever you do... be careful.
Generally java apps reside in the amr directory. i.e. if suc a directory exists on ur phone...
i wont be of much help to you since im not regular... but ask around... there are lots of ppl here to help...
best of luck.