It depends on what you consider the JVM. If you're just talking about something that can load class files and do some instruction interpretation (like this pro

It depends on what you consider the JVM. If you're just talking about something that can load class files and do some instruction interpretation (like this project) then that's one thing... if you're talking about implementing all of the JNI functions within the JVM standard library (awt, net) along with the concurrency primitives (conforming to the Java memory model?) then that is a significant multi-year, multi-developer project.