static class MonoThread {
  Thread t;
  
  boolean runIfNotRunning(final Runnable r) {
    ret run(r);
  }
  
  synchronized boolean run(final Runnable r) {
    if (t == null) {
      t = new Thread() {
        public void run() {
          try {
            r.run();
          } catch (Throwable e) {
            e.printStackTrace();
          } finally {
            synchronized(MonoThread.this) {
              t = null;
            }
          }
        }
      };
      t.start();
      return true;
    } else
      return false;
  }
}