What Java implementation?

OpenJDK is a mix of Java and C++, with long term roadmap to replace more and more with Java, also known as Project Metropolis.

IBM J9 is a mix of C++ and Java.

JikesRVM is bootstraped in Java.

Then there are PTC, Aicas, Websphere RealTime, J/Rockit, Azul (with LLVM integration), GraalVM (mostly Java), Ricoh JVM, Cisco JVM, Gemalto,...

I'm pretty sure it's largely classic C, /not/ C++.

I'm pretty sure that's 100% immaterial to the argument but from 8 seconds on Google, here: https://github.com/openjdk/jdk C++: 13.9% C: 5.4%

Or here: https://en.wikipedia.org/wiki/HotSpot "Written in C++, Assembly"

Or here: https://blogs.oracle.com/sundararajan/so-you-want-to-read-ho...

I should have said Perl to really bring out the pedants.

13.9% is hardly a big surface and I bet those C values come from C++ header files.

Also OpenJDK is just one implementation among several.

It was C++ at least in the 90s when I interviewed for the JVM compiler team.