if ((itemSet == null) || !(itemSet.getClass().equals(this.getClass()))) { return false; }
  public final boolean equals(Object itemSet) {    if (m_items.length != ((ItemSet)itemSet).m_items.length)      return false;    for (int i = 0; i < m_items.length; i++)      if (m_items[i] != ((ItemSet)itemSet).m_items[i])	return false;    return true;  }