Whole document tree
2.5. Main, contrib or non-free
About politics: packaging Java stuff changes nothing to the rules Debian uses to find if a program is free or not. Since there are not many free Java tools, keep in mind the following:
If your source package can compile (correctly) only with non-free tools (the only free Java compilers seem to be guavac, gcj and jikes, it cannot go to main. If your package itself is free, it must go to contrib.
If your binary package can run only with non-free virtual machines (the only free Java virtual machine seems to be kaffe - and the one included in libgcj), it cannot go to main. If your package itself is free, it must go to contrib.