I installed Eclipse. It is OK to run it in normal user account.
but when I run it as root(i.e. sudo eclipse)
It has error message:
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

I don't know what's the problem?

Also, When I try to run the written program..., it said cannot write and delete things. I think it is permission problem. And also, the write and delete is done on FAT32 FS.(/mnt/data). It seems that I cannot change the permission. But it is necessary for me. How can I do so that the program can have full permission on the files in FAT32 file system?

OK, first, you should not run anything as root. It's a huge security risk. Even if you PC is not networked, you should still not run anything as root, because one file that you delete wrongly will ruin your system. The error you are getting is exactly because of it... the system do not want you do run programs as root. Still, doing this would fix it:

Open a terminal then type:

xhost +

then login as root with su:

su

then try to fire up Eclipse again:

eclipse

The best way though, is to make sure that all your users can write to the FAT32 partition. To do that, you've to edit your /etc/fstab, adding the following line to it:

/dev/hda1 /mnt/data vfat uid=500,gid=500,umask=000,exec,dev,suid,rw 1 0

That's all. Hope it helps.

Regards!