Either Slashdot is full of trolls, or there is an extraordinary dearth of knowledge about Java on Slashdot. So much FUD....every... time.
If you are super worried about the performance of one particular algorithm you need to implement, by all means implement in C. If you have an application that actually does lots of stuff, use Java - it's likely to perform better than what you could create in C or C++ in the same time. And it will be much easier to support.
Generally, to write performant code in Java, don't try to write C++ and bitch about the fact that Java isn't C++; write good Java, let the JIT compiler do it's thing and go to the pub on a friday night instead.