How do you format the day of the month to say “11th”, “21st” or “23rd” (ordinal indicator)?

Question

I know this will give me the day of the month as a number (11, 21, 23):

SimpleDateFormat formatDayOfMonth = new Simple         


        

Answer 1

Using the new java.time package and the newer Java switch statement, the following easily allows an ordinal to be placed on a day of the month. One drawback is that this does not lend itself to canned formats specified in the DateFormatter class.

Simply create a day of some format but include %s%s to add the day and ordinal later.

ZonedDateTime ldt = ZonedDateTime.now();
String format = ldt.format(DateTimeFormatter
        .ofPattern("EEEE, MMMM '%s%s,' yyyy hh:mm:ss a zzz"));

Now pass the day of the week and the just formatted date to a helper method to add the ordinal day.

int day = ldt.getDayOfMonth();
System.out.println(applyOrdinalDaySuffix(format, day));

Prints

Tuesday, October 6th, 2020 11:38:23 AM EDT

Here is the helper method.

Using the Java 14 switch expressions makes getting the ordinal very easy.

public static String applyOrdinalDaySuffix(String format,
        int day) {
    if (day < 1 || day > 31)
        throw new IllegalArgumentException(
                String.format("Bad day of month (%s)", day));
    String ord = switch (day) {
        case 1, 21, 31 -> "st";
        case 2, 22 -> "nd";
        case 3, 23 -> "rd";
        default -> "th";
    };
    
    return String.format(format, day, ord);
}