Sometimes, when battling these issues, I wish the Smalltalk-style approach[1][2] was more popular/feasible. Basically, saving the entire state of the VM is a fundamental operation supported by the language. Only truly transient things like network connections require special effort. There are some echoes of this with things like Lua's Pluto/Eris, or serializable continuations in other languages (eg: Perl's Continuity…
You can surprisingly sort of do this in Java. Just create a lambda which will start the game at the current state when you call it.
Huh?