@xevilstar good to know that You want to contribute. First try to make app_java work again. From what I know it was not possible to build it with gcj so I removed the package.
I'm not the maintainer of that module and I don't have any interest in it. If you manage to fix it and make it work properly I can add the package for sure.
I managed to compile it without gcj using openjdk the memory leak problem is beyond my skills. I'd just need someone like the mantainer to intervene. Is there anyone that can contact him ?