Is there a way in Java to find out how many CPUs (or cores) are installed?

Question

I want to make some tuning for multithreaded program.

If I know how much threads can really work in parallel I can make the program much more effective.

Is there

Answer 1

You can use

Runtime.getRuntime().availableProcessors()

But its more of a best guess and even mentioned by the API

This value may change during a particular invocation of the virtual machine. Applications that are sensitive to the number of available processors should therefore occasionally poll this property and adjust their resource usage appropriately.