class DateRangeVisitor extends RangeVisitor {

    public void visit(Feature feature) {
        final Object firstValue = expr1.evaluate(feature);
        final Object secondValue = expr2.evaluate(feature);
        if (firstValue != null && secondValue != null) {
            final Date beginDate = (Date) firstValue;
            final Date endDate = (Date) secondValue;
            set.add(new DateRange(beginDate, endDate));
        }
    }

    public  DateRangeVisitor(String attributeTypeName1, String attributeTypeName2);

}