private void checkParentIdIsValid(int parentId) throws IndexOutOfBoundsException {
    final int recordsAllocatedSoFar = allocatedRecordsCount.get();
    if (!(NULL_ID <= parentId && parentId <= recordsAllocatedSoFar)) {
      throw new IndexOutOfBoundsException(
        "parentId(=" + parentId + ") is outside of allocated IDs range [0, " + recordsAllocatedSoFar + "]");
    }
  }
private void checkParentIdIsValid(int parentId)