I agree with the fact that java is slow.
Though I disagree that c++ isn't noticeably slower than c.
(sadly I don't have this experience, I'm not good enough to write anything cpu intensive
)
A friend of my fathers (and I suppose of mine) has been a programmer for many years. He wrote a large scale encryption program for some japanese company, he wrote it in C, ended up rewriting many of the basic functions such as memcpy because they were too slow. He also went back through his compiled code and rewrote pieces of the assembly to speed it up. Anything else would have simply been too slow.