How do I check the number of threads currently running in Java?

I'm looking for a way to see how many threads are currently running

>First > programmatically via windows

Solution

This will give you the total number of threads in the virtual machine:

int nbThreads =  Thread.getAllStackTraces().keySet().size();

Now, if you want all threads to be executing, you can do this:

int nbRunning = 0;
for (Thread t : Thread.getAllStackTraces().keySet()) {
    if (t.getState()==Thread.State.RUNNABLE) nbRunning++;
}

Here are the possible states: thread State javadoc

If you want to see that the running thread is not programming, but using Windows tools, you can use process explorer