Get Thread By Name

Question

I have a multithreaded application and I assign a unique name to each thread through setName() property. Now, I want functionality to get access to the threads

Answer 1

That's how I did it on the basis of this:

/*
    MIGHT THROW NULL POINTER
 */
Thread getThreadByName(String name) {
    // Get current Thread Group
    ThreadGroup threadGroup = Thread.currentThread().getThreadGroup();
    ThreadGroup parentThreadGroup;
    while ((parentThreadGroup = threadGroup.getParent()) != null) {
        threadGroup = parentThreadGroup;
    }
    // List all active Threads
    final ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();
    int nAllocated = threadMXBean.getThreadCount();
    int n = 0;
    Thread[] threads;
    do {
        nAllocated *= 2;
        threads = new Thread[nAllocated];
        n = threadGroup.enumerate(threads, true);
    } while (n == nAllocated);
    threads = Arrays.copyOf(threads, n);
    // Get Thread by name
    for (Thread thread : threads) {
        System.out.println(thread.getName());
        if (thread.getName().equals(name)) {
            return thread;
        }
    }
    return null;
}

Answer 2

An iteration of Pete's answer..

public Thread getThreadByName(String threadName) {
    for (Thread t : Thread.getAllStackTraces().keySet()) {
        if (t.getName().equals(threadName)) return t;
    }
    return null;
}

Answer 3

I like the HashMap idea best, but if you want to keep the Set, you can iterate over the Set, rather than going through the setup of converting to an array:

Iterator<Thread> i = threadSet.iterator();
while(i.hasNext()) {
  Thread t = i.next();
  if(t.getName().equals(threadName)) return t;
}
return null;

Answer 4

You can find all active threads using ThreadGroup:

• Get your current thread's group
• Work your way up the threadgroup hierarchy by calling ThreadGroup.getParent() until you find a group with a null parent.
• Call ThreadGroup.enumerate() to find all threads on the system.

The value of doing this completely escapes me ... what will you possibly do with a named thread? Unless you're subclassing Thread when you should be implementing Runnable (which is sloppy programming to start with).