[AtlasBarfed]

Since no one is replying to your actual question:

The JVM takes bytecode and generates assembly for execution. It also profiles that code and improves it over time.

Sometimes long running java bytecode will be faster than statically compiled C++. In many/most cases, long running Java code on good JVM will reasonably close to C++ for some measures of "reasonable".

Garbage collection pauses, memory usage, JVM startup/warmpup is all more detrimental to Java in the speed comparison.

But "quite slow" basically, to me, implies it is 10-100x slower than C++. Sure you can come up with various benchmarks (lies, damn lies, and benchmarks) to make some corner case.

In general, the JVM is probably about 2-3x slower than C++ compiled code. It certainly is not "quite slow".