get date format by locale

Question

I need a method whom I can pass locale (and style, probably), and who should return me date-formatting string. For example getDateFormatString(new Locale("en-US"), FormatStyle.SHORT) would return "M/dd/yy".

It is not enough for me to use something like DateTimeFormatter.ofLocalizedDate(FormatStyle.SHORT).withLocale(locale); for parsing, because I also need to parse format variations, for example to interpret M/dd as date in current year, so I want to make variations on original format string.

Answer 1

tl;dr

LocalDate currentYearAtGivenMonthDay =

Year.now( 
    ZonedId.of( "America/Montreal" )
).atMonthDay(
    MonthDay.parse( "1/7" , DateTimeFormatter.ofPattern( "M/d"
) )

Details

The java.time classes have some very specific types.

MonthDay

For your month-day, use the MonthDay class. Use a DateTimeFormatter to specify any non-standard (ISO 8601) formatted input strings.

DateTimeFormatter f = DateTimeFormatter.ofPattern( "M/d" );
MonthDay md = MonthDay.parse( yourInput , f );

Assign a year to get a LocalDate .

LocalDate ld = md.atYear( 2017 );

To determine current year instead of hard-coding a year number, use Year class. Specify a time zone as for any given moment the date varies around the globe by zone, and therefore the year can vary around December 31 to January 1.

ZoneId z = ZonedId.of( "America/Montreal" );
Year currentYear = Year.now( z );
LocalDate ld = currentYear.atMonthDay( md );

Similar types include YearMonth and Year and Month .

Also peruse the ThreeTen-Extra project for more classes that work with java.time.

DateTimeFormatterBuilder

For complicated variations not possible by formatting patterns, consider building up a DateTimeFormatter using the DateTimeFormatterBuilder . Search Stack Overflow for discussion and examples.