First, have a look at the website of HP (www.hp.com). You can download JDK versions for HP-UX there. I know that there is at least a version 1.2.2 JDK for HP-UX. For J2EE support, there are many application servers that work on HP-UX. I've used BEA Weblogic 5.1 on HP-UX, and version 6.0 or 6.1 should also work.
BEA Weblogic 6.1 supports the newest version of the J2EE API's, upto version 1.3 beta.
Jesper