Firstly, you're not in RedHat or Mandrake so try not to run RPMs when you have don't have to--besides, installing from source is more fun.
Secondly, I just downloaded the same package for Slackware 8.1 last night, but it was the source package (or was it a .bin file) and it installed flawlessly. Anyway, don't get the RPM.
Thirdly, if you absolutely must have a file and it only comes in RPM format, you can use:
rpm2tgz <filename>
I think that's the right syntax,
man rpm2tgz to be sure. Also, don't get the RPM if you have tarballs or Slackpacks available to you.
I would go back to
http://java.sun.com/linux/ and get the non-RedHat/Mandrake version. Then, I'd rm -f j2re-1_4_1_02-fcs-linux-i586.rpm just for good measure.
If you need any help, let me know.