Well, I'm not that familiar with current versions of J++. You do realize, don't you, that the MS version of
Java is stuck in a time warp with the 1.1.4 version of the JDK, and will not be updated, for a variety of reasons.
So any work you do with J++ is not going to be "mainstream" Java, and certainly won't work with JDK 1.3. I'd suggest you look at a more Java-friendly
IDE; there are dozens to choose from, and many have free versions available.