Sounds like you might have wiped the contents of the PATH variable. That's why you don't see the commands.

Login as root from a text console (ALT+F2) and do this command:

echo $PATH

You should have at least these directories in the path:

/bin:/usr/bin:/usr/X11R6/bin

You need to edit /etc/profile and fix the assignment to the PATH variable. Make sure you use colon ( : ) as a separator. It is a common mistake for windows users to use simicolon instead.

You can still invoke the commands by specifying the full path.

Hopefully you know how to use the vi editor. If you do then just do

/bin/vi /etc/profile

fix the profile.

Optimally your PATH should contain other directories including the direcotry for Java binaries.

Before you edit any files it is a good practice to make a copy of the file just in case you need to restore it.