public IntervalListMonth(ColumnGroup columnGroup) {
super(columnGroup);
intervalMap = new HashMap<Integer, Interval>();
Month firstMonth = columnGroup.getFirstMonthOfYear();
int monthIndex = firstMonth.getIndex();
Month[] months = Month.getAll();
for (int i = 0; i < months.length; i++) {
Month month = months[monthIndex];
Interval interval = new Interval(month.toString());
this.add(interval);
intervalMap.put(monthIndex, interval);
monthIndex = Month.nextIndex(monthIndex);
}