That has been discussed N+1 times already. The Java 1.4.2 server VM is actually almost as fast as C++, in most fields like integer, floating-point & IO performance. It is supposed to be faster than C++ when creating objects.

Ask google for some benchmark results.

Java's VM is not an interpreter. The code is really compiled and repeated tasks don't require repeated compiling.

The speed difference of the Swing GUI compared to a GUI using standard Windows widgets is noticeable, of course. Java GUIs always seem to be a little slower reacting to mouse-clicks.