How do you format a date range in Java?

Question

I have two dates - a start and an end. I'd like to format them so that if the months match, they collapse to something like "20-23 AUG" and still format correctly if they break over the end of the month, like "20 SEP - 1 OCT". Are there any libraries out there for accomplishing this, or would I have to hand code rules for displaying ranges of dates using individual DateFormats?

Answer 1

Checkout java's SimpleDateFormat class. You can construct a SimpleDateFormat passing you're date pattern as a String.

Answer 2

To add to Jeroen's answer, you're going to use SimpleDateFormat twice, once for each end of the range.

Answer 3

There is not such type as day range in Java by default, so none of the DateFormats apply to string representation of this case.

The best in my opinion, well be creation of type TimeSpan or TimeDiff and override method to string. Or as You suggested create a DateFormmater if you need two also parsing.

Answer 4

Here's a solution using JodaTime, the best library for dealing with dates in Java (last time I checked). The formatting is simple and could no doubt be improved by using custom DateFormatter implementations. This also checks that the year is the same, but doesn't output the year, which could be confusing.

import org.joda.time.DateTime;

public class DateFormatterTest {

    public static void main(String[] args) {

        DateTime august23rd = new DateTime(2010, 8, 23, 0, 0, 0, 0);
        DateTime august25th = new DateTime(2010, 8, 25, 0, 0, 0, 0);
        DateTime september5th = new DateTime(2010, 9, 5, 0, 0, 0, 0);

        DateFormatterTest tester = new DateFormatterTest();
        tester.outputDate(august23rd, august25th);
        tester.outputDate(august23rd, september5th);

    }

    private void outputDate(DateTime firstDate, DateTime secondDate) {
        if ((firstDate.getMonthOfYear() == secondDate.getMonthOfYear()) && (firstDate.getYear() == secondDate.getYear())) {
            System.out.println(firstDate.getDayOfMonth() + " - " + secondDate.getDayOfMonth() + " " + firstDate.monthOfYear().getAsShortText());
        } else {
            System.out.println(firstDate.getDayOfMonth() + " " + firstDate.monthOfYear().getAsShortText() + " - " + secondDate.getDayOfMonth() + " " + secondDate.monthOfYear().getAsShortText());
        }
    }
}

Output:

23 - 25 Aug

23 Aug - 5 Sep

Answer 5

I was disappointed with the answers that didn't seem to read the question. Joda time didn't work in GWT and neither does SimpleDateFormat. Anyway, I already knew about DateTimeFormat in GWT. The main issue is that date objects getMonth() function is deprecated, and there doesn't seem to be a good way to compare months and/or years. This solution doesn't include year checking (which could be easily added by changing the monthFormatter), but that's not important for my case.

public final class DateUtility
{
    public static final DateTimeFormat MONTH_FORMAT = DateTimeFormat.getFormat("MMM");
    public static final DateTimeFormat DAY_FORMAT = DateTimeFormat.getFormat("dd");
    public static final DateTimeFormat DAY_MONTH_FORMAT = DateTimeFormat.getFormat("dd MMM");

    public static final String DASH = " - ";

    /**
     * Returns a "collapsed" date range String representing the period of time
     * between two Date parameters. Example: August 19 as a {@code startDate}
     * and August 30 as an {@code endDate} will return "19 - 30 AUG", August 28
     * as a {@code startDate} and September 7 as an {@code endDate} will return
     * "28 AUG - 07 SEP". This means if you pass this two dates which cannot
     * collapse into a shorter form, then the longer form is returned.  Years
     * are ignored, and the start and end dates are not checked to ensure we
     * are not going backwards in time (Aug 10 - July 04 is not checked).
     * 
     * @param startDate
     *            the start Date in the range.
     * @param endDate
     *            the end Date in the range.
     * @return a String representation of the range between the two dates given.
     */
    public static String collapseDate(Date startDate, Date endDate) {
        String formattedDateRange;

        // Get a comparison result to determine if the Months are the same
        String startDateMonth = MONTH_FORMAT.format(startDate);
        String endDateMonth = MONTH_FORMAT.format(endDate);

        if (startDateMonth.equals(endDateMonth))
        {
            formattedDateRange = DAY_FORMAT.format(startDate) + DASH
                    + DAY_MONTH_FORMAT.format(endDate).toUpperCase();
        }
        else
        {
            // Months don't match, split the string across both months
            formattedDateRange = DAY_MONTH_FORMAT.format(startDate).toUpperCase()
                    + DASH + DAY_MONTH_FORMAT.format(endDate).toUpperCase();
        }
        return formattedDateRange;
    }
}