It's not a directly mappable to a register-based microprocessor but it's directly mappable to a stack-based microprocessor.

e.g. The PSC 1000 microprocessor (1994) could run Java directly: https://en.wikipedia.org/wiki/Ignite_(microprocessor)

Stack-based microprocessors tend to perform worse than register-based ones and I assume there wasn't a huge reason to develop a Java-on-chip for a "Java computer.” (1) It would have not run non-Java software easily and (2) the future of stack-based microprocessors wasn't as bright.