Kaffee is a Java virtual machine alright (and also a fast Java compiler). What it lacks are amiga specific AWT classes, so all you get is console/shell based in and output. No graphics. And that's the main problem.
Holger Kruse was working on a Java implementation (including AWT), but had to stop when he started working for REBOL.
So, yes, you're probably stuck with your PC. The only thing I tried once was using the JavaVM of (an older version of) Netscape under Shapeshifter (well, I remember it worked once, but it was a pain in the ass to get this damn thing online).
