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

// https://github.com/google/guava
import static com.google.common.base.Preconditions.*;

String getDayOfMonthSuffix(final int n) {
    checkArgument(n >= 1 && n <= 31, "illegal day of month: " + n);
    if (n >= 11 && n <= 13) {
        return "th";
    }
    switch (n % 10) {
        case 1:  return "st";
        case 2:  return "nd";
        case 3:  return "rd";
        default: return "th";
    }
}

The table from @kaliatech is nice, but since the same information is repeated, it opens the chance for a bug. Such a bug actually exists in the table for 7tn, 17tn, and 27tn (this bug might get fixed as time goes on because of the fluid nature of StackOverflow, so check the version history on the answer to see the error).

There is nothing in JDK to do this.

  static String[] suffixes =
  //    0     1     2     3     4     5     6     7     8     9
     { "th", "st", "nd", "rd", "th", "th", "th", "th", "th", "th",
  //    10    11    12    13    14    15    16    17    18    19
       "th", "th", "th", "th", "th", "th", "th", "th", "th", "th",
  //    20    21    22    23    24    25    26    27    28    29
       "th", "st", "nd", "rd", "th", "th", "th", "th", "th", "th",
  //    30    31
       "th", "st" };

 Date date = new Date();
 SimpleDateFormat formatDayOfMonth  = new SimpleDateFormat("d");
 int day = Integer.parseInt(formatDateOfMonth.format(date));
 String dayStr = day + suffixes[day];

Or using Calendar:

 Calendar c = Calendar.getInstance();
 c.setTime(date);
 int day = c.get(Calendar.DAY_OF_MONTH);
 String dayStr = day + suffixes[day];

Per comments by @thorbjørn-ravn-andersen, a table like this can be helpful when localizing:

  static String[] suffixes =
     {  "0th",  "1st",  "2nd",  "3rd",  "4th",  "5th",  "6th",  "7th",  "8th",  "9th",
       "10th", "11th", "12th", "13th", "14th", "15th", "16th", "17th", "18th", "19th",
       "20th", "21st", "22nd", "23rd", "24th", "25th", "26th", "27th", "28th", "29th",
       "30th", "31st" };

private String getCurrentDateInSpecificFormat(Calendar currentCalDate) {
    String dayNumberSuffix = getDayNumberSuffix(currentCalDate.get(Calendar.DAY_OF_MONTH));
    DateFormat dateFormat = new SimpleDateFormat(" d'" + dayNumberSuffix + "' MMMM yyyy");
    return dateFormat.format(currentCalDate.getTime());
}

private String getDayNumberSuffix(int day) {
    if (day >= 11 && day <= 13) {
        return "th";
    }
    switch (day % 10) {
    case 1:
        return "st";
    case 2:
        return "nd";
    case 3:
        return "rd";
    default:
        return "th";
    }
}