static void listUserThreadsWithStackTraces() {
  printAsciiHeading("Threads");
  Map<Thread, StackTraceElement[]> threadMap = Thread.getAllStackTraces();
  int n = 0;
  for (Thread t : threadMap.keySet()) {
    ThreadGroup g = t.getThreadGroup();
    if (g != null && g.getName().equals("system")) continue;
    ++n;
    print(t);
    for (StackTraceElement e : threadMap.get(t)) {
      print("  " + e);
    }
    print();
  }
  print(n + " user threads.");
}