static jint get_vm_thread_count() {

  {- -------------------------------------------
  (1) VmThreadCountClosure を使ってスレッド数を数え, その結果をリターンする.
      ---------------------------------------- -}

      VmThreadCountClosure vmtcc;
      {
        MutexLockerEx ml(Threads_lock);
        Threads::threads_do(&vmtcc);
      }

      return vmtcc.count();
    }