How to format YearMonth and MonthDay depending on a Locale?

Question

Formatting a LocalDate in Java 8 using a specific Locale can be achieved like this:

DateTimeFormatter.ofLocalizedDate(FormatStyle.S         


        

Answer 1

Solution provided by gevorg is probably the simplest solution if you will use a limited list of Locale.

If you want to make it work with any Locale I would suggest to get a locale pattern and then remove the parts you are not interested in, once you have this pattern you should remove the part you are not interested in and use the resulting pattern to create your own DateTimeFormatter.

This is a full example of the idea explained above for MonthDay. In order to use it for YearMonth replace keep.add('d') with keep.add('y'). (and of course MonthDay with YearMonth)

ArrayList locales = new ArrayList();
locales.add(Locale.ENGLISH);
locales.add(Locale.GERMAN);
locales.add(new Locale("es", "ES"));
locales.add(Locale.US);
ArrayList styles = new ArrayList();
styles.add(FormatStyle.SHORT);
styles.add(FormatStyle.MEDIUM);
styles.add(FormatStyle.LONG);
styles.add(FormatStyle.FULL);
ArrayList keep = new ArrayList();
keep.add('d');
keep.add('M');

for (FormatStyle style : styles) {
    for (Locale myLocale : locales) {
        String myPattern = DateTimeFormatterBuilder.getLocalizedDateTimePattern(style, null, IsoChronology.INSTANCE, myLocale);

        boolean separator = false;
        boolean copy = true;
        String newPattern = "";
        for (char c : myPattern.toCharArray()) {
            if (c == '\'') {
                separator = !separator;
            }
            if (!separator) {
                if (Character.isAlphabetic(c)) {
                    if (keep.contains(c)) {
                        copy = true;
                    } else {
                        copy = false;
                    }
                }
            }
            if (copy) {
                newPattern = newPattern + c;
            }
        }

        char lastChar = newPattern.charAt(newPattern.length() - 1);
        while (!keep.contains(lastChar)) {
            if (lastChar == '\'') {
                newPattern = newPattern.substring(0, newPattern.length() - 1);
                newPattern = newPattern.substring(0, newPattern.lastIndexOf('\''));
            } else {
                newPattern = newPattern.substring(0, newPattern.length() - 1);
            }
            lastChar = newPattern.charAt(newPattern.length() - 1);
        }

        System.out.println(DateTimeFormatter.ofPattern(newPattern, myLocale).format(YearMonth.now()));
    }
    System.out.println();
}

The output would be:

6/30
Jun 30
June 30
June 30

30.06
30.06
30. Juni
30. Juni

30/06
30-jun
30 de junio
30 de junio

6/30
Jun 30
June 30
June 30

And for YearMonth:

6/16
Jun 2016
June 2016
June 2016

06.16
06.2016
Juni 2016
Juni 2016

06/16
jun-2016
junio de 2016
junio de 2016

6/16
Jun 2016
June 2016
June 2016