How do I obtain the number of days within a given month using Joda-Time?

Question

30 days hath September,
   April, June and November,
 All the rest have 31,
   Excepting February alone
(And that has 28 days clear,
   With 29 in each leap year).
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Answer 1

Yes, although it's not as pretty as it might be:

import org.joda.time.*;
import org.joda.time.chrono.*;
import org.joda.time.field.*;

public class Test {
    public static void main(String[] args) {
        GregorianChronology calendar = GregorianChronology.getInstance();
        DateTimeField field = calendar.dayOfMonth();

        for (int i = 1; i < 12; i++) {
            LocalDate date = new LocalDate(2010, i, 1, calendar);
            System.out.println(field.getMaximumValue(date));
        }
    }
}

Note that I've hard-coded the assumption that there are 12 months, and that we're interested in 2010. I've explicitly selected the Gregorian chronology though - in other chronologies you'd get different answers, of course. (And the "12 month" loop wouldn't be a valid assumption either...)

I've gone for a LocalDate rather than a DateTime in order to fetch the value, to emphasize (however faintly :) that the value doesn't depend on the time zone.

This is still not as simple as it looks, mind you. I don't know off-hand what happens if use one chronology to construct the LocalDate, but ask for the maximum value of a field in a different chronology. I have some ideas about what might happen, knowing a certain amount about Joda Time, but it's probably not a good idea :)