this.frqReference = frqReference;
  }

  /** Loops continuously, pulling references off the queue and cleaning them up. */
  @SuppressWarnings("InfiniteLoopStatement")
  @Override
  public void run() {
    while (true) {
      try {
        if (!cleanUp(queue.remove())) {
          break;
        }
      } catch (InterruptedException e) {
        // ignore