I had no trouble changing my $PATH variable to include the java directory, it's as easy as issuing the following command:

PATH=$PATH:/usr/java/jre1.3.1/bin/

I was however unable to EXPORT my $PATH variable (meaning, whenever I closed the terminal/rebooted/etc my $PATH variable would return to it's original state). I also use Mandrake (but i'm using version 8.1 beta 2) and I think it's a bug or something. Anyways, I got it to work by creating a symbolic link to java in one of the directories listed in the $PATH variable. How did I do that? Well, since I am a Linux newbie, I actually had a little trouble with it. First i searched for java by using the following command:

whereis java

That would tell me which directory java was installed in (from what I read, I believe java is located in "/usr/java/jre1.3.1/bin/" for your system). Then I issued the following command:

echo $PATH

That will display all of the directories in the $PATH variable (which are all separated by a colon) Then I picked of those directories and made it the current directory. Then I created the symbolic link by issueing the following command:

ln -s /usr/java/jre1.3.1/bin/java java

This should work IF
1. /usr/java/jre1.3.1/bin/ is the directory where java is located
2. You issued the command while in a directory which is in your $PATH environment variable.

Hope that helps. If you find out how to export an environment variable so that it's value is saved, please let me know.