HotSpot is a JIT engine separated in parts C1,C2. This is part of the OpenJDK codebase and part of OracleJDK, Zulu and RedHat's shipping OpenJDK version. The C2

HotSpot is a JIT engine separated in parts C1,C2. This is part of the OpenJDK codebase and part of OracleJDK, Zulu and RedHat's shipping OpenJDK version. The C2 hotspot layer might be removed in favour of graal[1] in the mainline over next years, but that is open too. IBM has their own in J9 JIT infra which is also (being made) open source. [2] Most shops use OracleJDK which is more habbit than anything else as the other OpenJDK derived versions such as Azul Zulu or the ones in RedHat cent-os are very much from the same branch and also pass the TCK. [1] https://github.com/graalvm/graal https://github.com/graalvm/graal [2] https://archive.fosdem.org/2017/schedule/event/openj9/ https://archive.fosdem.org/2017/schedule/event/openj9/