DateTimeFormatter to serialize LocalDate as ordinal 1st/2nd/3rd of a month

Question

I'd like to display LocalDate as:

first day: 1st;
second day: 2nd;
third day: 3rd;
all rest days: Nth.

e.g. 1980-10-1 as 1st Oct 1980

I'm able to serialize it excluding the first 3 days using DateTimeFormatter.ofPattern("dth MMM yyyy"). Since the first 3 days have a different pattern than the rest days, how to construct the formatter to serialize also the first 3 days?

Also, be careful to account for "21st", "22nd", "23rd", and "31st" that don't follow the "th" pattern — Krease, Nov 20 '18 at 17:44
See https://stackoverflow.com/questions/26337836/how-to-format-the-current-date-with-suffix-to-superscript — Krease, Nov 20 '18 at 17:47
[here](https://stackoverflow.com/a/50369812/836214) is another good answer similar to the one below — Krease, Nov 20 '18 at 18:49

Arnault Le Prévost-Corvellec · Accepted Answer · 2018-11-20T17:55:49.170

3

here is what you are searching : https://docs.oracle.com/javase/8/docs/api/java/time/format/DateTimeFormatterBuilder.html#appendText-java.time.temporal.TemporalField-java.util.Map-

and here is an exemple :

DateTimeFormatterBuilder builder = new DateTimeFormatterBuilder();
Map<Long, String> mapToRoman = new HashMap<>();
mapToRoman.put(1L, "1st");
mapToRoman.put(2L, "2nd");
mapToRoman.put(3L, "3rd");
mapToRoman.put(4L, "4th");
// continue to map all available days in a month
builder.appendText(ChronoField.DAY_OF_MONTH, mapToRoman );
builder.append(DateTimeFormatter.ofPattern(" MM yyyy", Locale.US));
DateTimeFormatter formatter = builder.toFormatter();

edited Nov 20 '18 at 17:55

answered Nov 20 '18 at 17:39

Arnault Le Prévost-Corvellec

495
2
9

1

be careful to account for "21st", "22nd", "23rd", and "31st" that don't follow the "th" pattern – Krease Nov 20 '18 at 17:44
yes of course this is just a sample^^ even the "th" isn't present here – Arnault Le Prévost-Corvellec Nov 20 '18 at 17:54
1

This is a really good answer. A little fix: One M is missing in the month part: builder.append(DateTimeFormatter.ofPattern(" **MMM** yyyy", Locale.US)); – Adrián Paredes Nov 20 '18 at 18:22
Is there a simpler way to just add 4 patterns (since it has only 4 different patterns) instead of adding all of 31 days? – LunaticJape Nov 20 '18 at 18:53
@LunaticJape - Sort of - a similar answer [here](https://stackoverflow.com/a/50369812/836214) uses the same logic, but puts coverage for all 31 days in a few lines – Krease Nov 20 '18 at 23:18

DateTimeFormatter to serialize LocalDate as ordinal 1st/2nd/3rd of a month

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