C++ can be 5x faster than java if both programs are well-tuned — A ball-park estimate given by Stroustrup.
The c++ code is often written like java code, using lots of pointers, virtual functions, no inline, perhaps with too many heap allocations (STL containers) rather than strictly-stack variables .
Many other benchmarks are similarly questionable. These new languages out there are usually OO and rely on GC + pointer indirection. If you translate their code to C++, the resulting c++ code would be horribly inefficient, not taking advantage of c++ compiler’s powers. An expert c++ developer would rewrite everything to avoid virtual functions and favor local variables and inline, and possibly use compile-time programming. The binary would usually become comparable in benchmark. The c++ compiler is more sophisticated and have more optimization opportunities, so it usually produces faster code.