Is there something equivalent to OmniCppComplete for java in vim ? I know of eclim but I think it is overkill for such a simple feature.
Also found VJDE - http://www.vim.org/scripts/script.php?script_id=1213 - Need to evaluate which one is better/more up-to-date
Seems you have some options for code-completion above.
I would recommend also grabbing a copy of TagList, which provides a sidebar displaying the structure of your current file.
The ctags which TagList uses can also be used for fast navigation in Vim. Ctrl+] over the text "curiousMethod()" should take you to the definition of that method.
Silly question, but is there any reason you are not using an IDE. Many IDEs have a plugin so you can perform vi like operations. IDEs also allow you to run, debug or even profile your application with a single click or key.
I used to only use vi for development and didn't see the point of using an IDE, but when I did start using an IDE, I couldn't believe I had resisted using one. (That was in the year 2000 BTW)