static S renderUserThreadsWithStackTraces() {

  ret renderUserThreadsWithStackTraces(mapWithout(Thread.getAllStackTraces(), currentThread()));

}

static S renderUserThreadsWithStackTraces(Map<Thread, StackTraceElement[]> threadMap) {

  ret renderUserThreadsWithStackTraces(threadMap, "thread");

}

static S renderUserThreadsWithStackTraces(Map<Thread, StackTraceElement[]> threadMap, S threadDescription) {

  new StringBuilder bufRunnable;

  new StringBuilder bufWaiting;

  int nRunnable = 0, nWaiting = 0, nSystem = 0;

  for (t, stackTrace : threadMap) {

    bool runnable = isThreadRunnable_x(t, stackTrace);

    var buf = runnable ? bufRunnable : bufWaiting;

    ThreadGroup g = t.getThreadGroup();

    if (g != null && g.getName().equals("system"))

      continue with ++nSystem;

    if (runnable) ++nRunnable; else ++nWaiting;

    printTo(buf, t);

    for (StackTraceElement e : threadMap.get(t))

      printTo(buf, "  " + e);

    printTo(buf);

  }

  ret asciiHeading2(n2(nRunnable, "runnable " + threadDescription))

      + "\n" + bufRunnable

    + asciiHeading2(n2(nWaiting, "sleeping " + threadDescription)

      + " (+" + n2(nSystem, "system thread") + ")")

      + "\n" + bufWaiting;

}