You're in the wrong forum. Try posting in the Tech Talk/Unix and Linux forum for problems with Linux. This forum is about problems related to developing software with Java.

well, you're not using the official JDK there.
Check your $PATH and $JAVA_HOME environment settings and make sure they point to your JDK installation.
As it is you're pointing to gcj which is to put it bluntly a disaster, I'm surprised you got anything to compile and/or run under it at all.

how to set the $PATH..i have no idea,plz help!

read some Unix tutorials.
This has nothing to do with Java per se, but core operating system knowledge.

To view what's currently in your PATH or JAVA_HOME variable:
You'll see a list of paths seperated by colons. If the path where you installed Java is not in either of these, you should probably add them like so (add them to both, just to be safe):
Of course, these paths are only temporary. To permenantly add them, you'll need to edit your .bash_profile or some other startup script that your distro uses. Again, refer to documentation for exact instructions.

i'm sorry for posting in the wrong forum

And thanx to all your help,my java is running now.I had to set $PATH & $JAVAHOME /etc/profile.Thanx a lot