I think the general consensus is that Java is slower than C++, but offers the advantage of easy cross-compatibility between OSes. C++ also is slightly more complicated to learn, but yields faster programs.
If we were talking about embedded systems, C++ would win hands down just because of the sheer amount of overhead required for Java.
Ultimately it doesn't matter for the kind of stuff we're doing here at the GMG. I don't think anybody here really cares if we can get in one more calculation in a cycle. However these things matter when you're studying computers and how to make them faster.
Ghost