[Santosh83]

You could write a Java based virtual kernel designed to run within the JVM and manage child processes I suppose, but what is the real world utility of such a thing?

Almost everything to do with kernels is about directly writing to memory addresses and ports and these things can't be done with a managed language, at least not without a significant runtime doing all the grunt work, at which point you'll need to understand much of the runtime's internals and at that point, you may as well have started out with a small C/C++/Rust kernel, plenty of which exist.