Welcome to JavaRanch!
In your haste to come in and ask a question, you seem to have missed reading our
policy on display names, which quite clearly states that you must use a real (sounding) first and last name for your display name -- no joke names, "handles," or last initials are acceptable. You can fix your display name
here. Thanks for your cooperation!
Now, as to your questions: the only limits on number of threads are practical ones -- i.e., how much memory there is for thread stacks, and how many threads the OS supports. And as to the question about "the mutex" -- this is an implementation detail that is unspecified by the JVM specification.