jmk & .jar files

Trying to get jmk to work on my Debian box. I installed the jmk and kaffe packages, but whenever I run jmk it says "No manifest found in '/usr/share/java/java.jar", but that file is empty, I installed fastjar, since the description said it creates jar files, but looks kind of confusing. Anybody know how to create them, or if anyone has it working on a Debian 3.0 machine who can send me their java.jar file? :) Thanks.