"Hard Realtime Garbage Collection in Modern Object Oriented Programming Languages."
https://www.amazon.com/Realtime-Collection-Oriented-Programm...
The author is one of the founders of Aicas real time JVM, https://www.aicas.com/wp/products-services/jamaicavm/
"Distributed, Embedded and Real-time Java Systems"
https://link.springer.com/book/10.1007/978-1-4419-8158-5
PTC is the other company alongside Aicas, that still sells real time Java systems, https://www.ptc.com/en/products/developer-tools/perc
IBM J9 has the evolution of the Metronome GC, https://www.researchgate.net/publication/220829995_The_Metro...
And it has extensions for value types, via packed object data, https://www.ibm.com/docs/en/sdk-java-technology/7.1?topic=ob...
Someone else already referred Azul, they also have extensions for value types, called object layouts, https://www.slideshare.net/AzulSystems/jvm-language-summit-o...
Then there are special flavours like microEJ or the Android Java snowflake.
