Priority

The JVM scheduler is a fixed priority scheduler.
Every thread has a priority number. Bigger is better.
The scheduler chooses the runnable thread with the highest priority for execution. When it stops, yields, or becomes not runnable then a lower priority thread starts executing.
If two threads of the same priority are waiting the scheduler chooses one of them to run in a round-robin fashion.
A thread will run until:
- A higher priority thread becomes runnable, i.e., its preemptive.
- It yields, or its run method exits.
- On systems that support time-slicing, its time allotment has expired.
The scheduler does violate priority in order to avoid starvation.
On a system without time-slicing, a selfish thread will only stop for a higher-priority thread (an equal-priority thread might have to wait a long time.)
On systems with time-slicing (Unix, NT, W95) same-priority threads are interleaved.
Remember: even if you have multiple threads, you still only have one CPU. Be nice!