You can argue Java is faster than C, but this comment did a good job summarizing the results:

A langauge in and of itself does not determine the speed. It's how that language is implemented/compiled. There's no reason why Java SHOULD be slower as long as it is compiled to the machine's architecture, and not to byte code. ... but then that destroys the purpose of Java.

What's important to note is that the differences introduced by the VM and the rest of Java's overhead are small enough now that, for headless applications, poor coding can easily bridge the difference. There's no huge, glaring reason to use C++ over Java for headless apps, and when you want your server code to be portable crossplatform you'll find a huge, glaring reason to use Java.

Now what this study obviously doesn't deal at all with GUI'd applications, and Sun's Swing in particular does nothing to help Java's reputation as a slow technology. There's a relatively interesting discussion at called Swing Usability that points out some of these shortcomings. What the Swing team doesn't seem to understand is that slower than native means slow to most users. And just like the comments in the slashdot thread, as long as you put a compatibility layer between code and execution, you're going to be slower by definition. With Swing, simple to overlook unoptimized coding practices do not cannot spell the difference between implementations.