Raising the priority of a process or
thread will only make it go faster if it is doing a CPU-intensive task
and there is some other process or thread that is also doing a CPU-intensive task. If that is the case, what is the other process or thread that's using the CPU?
Raising the priority will not help if your application is blocked waiting for I/O, network, database etc. But putting tasks onto separate threads could help, by allowing useful work to be done during waits for I/O etc.
Raising the priority of a process or thread above the normal priority can be very dodgy. If your high-priority process or thread begins a long-running CPU-intensive task, then the whole O/S will likely become unresponsive. You may even have trouble killing your process, because you can't get at the Task Manager or command shell.
As an alternative to raising the priority of your process, you could reduce the priority of the other process(es). That's often safer.
Raising the priority of an ordinary Java process to Windows Realtime setting is almost certainly insane. You'll just hang your machine, most likely.
By the way, you generally can't do that sort of thing with Pure Java. Depending on how your machine is configured, you may or may not be able to do it with native code or external programs.
[ December 07, 2007: Message edited by: Peter Chase ]