How to convert two digit year to full year using Java 8 time API

Question

I wish to remove the Joda-Time library from my project.

I am trying to convert a two digit year to full year. The following code from Joda-Time can fulfil the purpos

Answer 1

You need to provide default values for DAY_OF_MONTH and MONTH_OF_YEAR

DateTimeFormatter TWO_YEAR_FORMATTER = new DateTimeFormatterBuilder()
                .appendPattern("yy")
                .parseDefaulting(ChronoField.MONTH_OF_YEAR, 1)
                .parseDefaulting(ChronoField.DAY_OF_MONTH, 1)
                .toFormatter();

In addition,

Java-8 uses the range 2000-2099 per default, not like SimpleDateFormat the range -80 years until +20 years relative to today.

Full answer

Since you're parsing years only, in order to have '99' as '1999' your code should be like this:

DateTimeFormatter TWO_YEAR_FORMATTER = new DateTimeFormatterBuilder()
                .appendPattern("")
                .parseDefaulting(ChronoField.MONTH_OF_YEAR, 1)
                .parseDefaulting(ChronoField.DAY_OF_MONTH, 1)
                .appendValueReduced(ChronoField.YEAR_OF_ERA, 2, 2, LocalDate.now().minusYears(80))
                .toFormatter();