What kind of troubles do you have? On my machine (Ubuntu 12.04) I don't have any problem by using Java 7 using my config (https://github.com/alexott/emacs-configs/blob/master/rc/emacs-rc-cedet.el
java version "1.7.0_25"
Java(TM) SE Runtime Environment (build 1.7.0_25-b15)
Java HotSpot(TM) 64-Bit Server VM (build 23.25-b01, mixed mode)
I able to get name completion & navigation for java code using the semantic/db-javap.
P.S. I have separate branch of CEDET (https://github.com/alexott/cedet/tree/devel
) that I'm using for development of code, that will be later re-integrated into main branch. You can also try it if you want - it has some improvements for Maven & Ant project types.