I believe it is variable (depends on memory settings and such), but if you have the computer in question to test on, you can
test it out.
Additionally, the maximum number of threads, priority assigned and order of interrupts are undefined within the JVM specification. This is due to slight differences in implementation depending on the hardware and underlying OS. As a simple example, the same code running on the same JVM under the same version of Windows will handle interrupts and assign thread priority differently depending on the CPU being used.