Get all your Threads and Thread Groups

 
public void printOutThreadGroups()
{
    //create a thread
    Thread t = new Thread();
    //get the current thread
    Thread tt = t.currentThread();
    //get the thread group of current thread
    ThreadGroup tg = tt.getThreadGroup();
    ThreadGroup topMost = null;
    //find the topmost thread group
    while(tg != null)
    {
        topMost = tg;
        tg = tg.getParent();
    }
    //get an estimate of active thread groups under topMost
    int groupCount = topMost.activeGroupCount();
    //get an enumeration of thread groups under topMost
    ThreadGroup[] tgArray = new ThreadGroup[groupCount];
    topMost.enumerate(tgArray, true);
    //for every thread group under topMost, print out the 
active threads
    System.out.println("Top Most ThreadGroup: \""+topMost.getName()+
       "\" has the following Thread Groups:");
    System.out.println("**********************");
    for(int i=0; i<tgArray.length; i++)
    {
        ThreadGroup aThreadGroup = tgArray[i];
        int count = aThreadGroup.activeCount();
        //get an enumeration of threads in aThreadGroup
        Thread[] tArray = new Thread[count];
        aThreadGroup.enumerate(tArray, true);
        System.out.println("Thread Group: \""+aThreadGroup.getName()+
            "\" has the following threads: ");
       String indent = " ";
        for(int j=0; j<tArray.length; j++)
        {
            Thread aThread = tArray[j];
            System.out.println(indent +" \""+aThread.getName()+"\"");
            indent += " ";
        }
        System.out.println("**********************");
        tArray = null;
    }
    tgArray = null;
    t = null;
}