class DateColumn extends AbstractColumn<DateColumn, LocalDate> implements DateFilters,
        DateFillers<DateColumn>,
        DateMapFunctions,
        CategoricalColumn<LocalDate> {

  @Override
  public int countUnique() {
    IntSet ints = new IntOpenHashSet(size());
    for (int i = 0; i < size(); i++) {
      ints.add(data.getInt(i));
    }
    return ints.size();
  }

  private  DateColumn(String name, IntArrayList data);

}