setHead(headSentinel(queue.getArity()));
head = headSentinel(queue.getArity());
  public final void flushLocal() {    super.flushLocal();    if (head.NE(headSentinel(queue.getArity()))) {      closeAndEnqueueHead(queue.getArity());      setHead(headSentinel(queue.getArity()));    }  }