What is the relationship between number of CPU cores and number of threads in an app in java?

Question

I\'m new to java multi-threaded programming. The question that has came to my mind is that how many threads can I run according to the number of my CPU

Answer 1

That depends on what the threads are doing. The CPU is only able to do X things at once, where X is the number of cores it has. That means X threads at most can be active at any one time - however the other threads can wait their turn and the CPU will process them at appropriate moments.

You should also consider that a lot of the time threads are waiting for a response, or waiting for data to load, or a network message to arrive, etc so are not actually trying to do anything. These idle/waiting threads have very little load on the system.