java might run at a decent speed... Might, but probably won't (jk, sorry, I couldn't help myself...) [edit Grammarly decided to remove some text when fixing spelling...]
Java runs at 90% the speed of C for most common benchmarks. It uses 50x the RAM to do so. But you're dead wrong to think java is slow. The only reason physics game engines are written in C++ is because physics game engines are written in C++.
It's not 90%, more of several times slower: https://benchmarksgame-team.pages.debian.net/benchmarksgame/...
>The only reason physics game engines are written in C++ is because physics game engines are written in C++.
They are written in C++ because of latency requirements which are nearly impossible in GCed language.