@Override
  public int hashCode() {
    final int prime = 31;
    int result = super.hashCode();
    result = prime * result + ((collator == null) ? 0 : collator.hashCode());
    result = prime * result + ((field == null) ? 0 : field.hashCode());
    result = prime * result + (includeLower ? 1231 : 1237);
    result = prime * result + (includeUpper ? 1231 : 1237);
    result = prime * result + ((lowerTerm == null) ? 0 : lowerTerm.hashCode());
    result = prime * result + ((upperTerm == null) ? 0 : upperTerm.hashCode());
    return result;
  }