I realize that the Java "space" is part of Oracle's larger system, so you might not be able to directly act on this feedback, but I hope it's useful in the long run.
1) The Java forums (spaces) don't seem to be very active, yet they are broken into a large number of subcategories (sub-spaces). This might be OK if it weren't so painfully cumbersome and slow to navigate through those categories, at least for the purpose of looking for questions that I might be able to answer. It requires many clicks, and long waits for page loads. I'm using the system at 10PM EDT, so there should be very little traffic, at least generated from the U.S. It is way too slow.
2) There is no way to sort/filter the questions in order to find unanswered questions. If you want users to answer questions, please make it easy to do so.
3) The procedure to edit/update your display name seems clunky (too many clicks and different pages), and doesn't take effect right away. (I presume it's because display names are managed at some higher point in the framework/hierarchy, but a good UI would hide that from the user, instead of make us traverse internal structures.) I changed my email address and display name, logged back in (because for some lame reason I was forced to) then I still see my old email and display name in my profile. Yet when I tried to edit my display name again, the edit screen showed my correct/new name. So I waited. Ten minutes later it was sync'd. Clunky! It's just not excusable from a software giant. I realize these are large data sets and complex systems, but retail sites (e.g. Amazon) can do it smoothly, so I think/expect Oracle can too.
4) The use of terms like "spaces" and "subspaces" might sound novel and cool, but it is not normal, and slows understanding/navigation of your site. Please use more standard, well-understood terms, e.g. category, topic, forum, etc.
5) The web UI is pretty, but pages are slow to load, and slow to render. I'd prefer a speedy web site. We're fast-thinking Java developers after all, not retirees with time to kill.
6) Mixing content (blogs, docs, discussions, polls, and ideas) on the "Content" tab isn't very useful. If I want to answer some questions, it takes more clicks.
7) The info on the Overview tab seems to mostly overlap that of the Content tab. Both list questions and docs. The Overview should include info about the number of unanswered questions, for example. That would be useful "overview" information.
8) Intermediate "spaces" (those possessing sub-spaces) don't seem to support forum questions, but they do contain docs and polls. It's just weird. Why can't I ask a question at a general level. If that doesn't fit your model (which can be understandable), then why do docs and polls deserve to exist at intermediate tree levels?
9) Did I mention it's just too slow?
Sorry for the negative feedback. I do love Java, and I'm impressed by the quality of questions posted and the high rate of responses with good info, so there's some great potential here! :-)