Get a list of all threads currently running in Java

Question

Is there any way I can get a list of all running threads in the current JVM (including the threads not started by my class)?

Is it also possible to get the

Answer 1

Get a handle to the root ThreadGroup, like this:

ThreadGroup rootGroup = Thread.currentThread().getThreadGroup();
ThreadGroup parentGroup;
while ((parentGroup = rootGroup.getParent()) != null) {
    rootGroup = parentGroup;
}

Now, call the enumerate() function on the root group repeatedly. The second argument lets you get all threads, recursively:

Thread[] threads = new Thread[rootGroup.activeCount()];
while (rootGroup.enumerate(threads, true ) == threads.length) {
    threads = new Thread[threads.length * 2];
}

Note how we call enumerate() repeatedly until the array is large enough to contain all entries.