I’ve been working on a new front end for gcj. This front end
features strong typing in the representation of the internal model, a
hand-written recursive descent parser, and is intended to be easy to
extend to add support for generics and the other new Java features
(enhanced for loop and static imports are already implemented). It
is written in C++.

Currently it can successfully parse most of libgcj and Eclipse,
and resolve all the extends and implements
clauses. So, it already fixes one gcj bug. I’d estimate, though,
that it is only about 40% done at the moment.