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javatimejava-8localdate

LocalDate from YearMonth with nth DayOfWeek

I would like to convert a YearMonth to a LocalDate with the specified DayOfWeek, e.g. the second Tuesday of February 2019.

The following code throws a DateTimeException:

YearMonth yearMonth = YearMonth.of(2019, Month.FEBRUARY);
TemporalAdjuster secondTuesday = TemporalAdjusters.dayOfWeekInMonth(2, DayOfWeek.TUESDAY);

LocalDate date = LocalDate.from(yearMonth).with(secondTuesday);

In order to make my code work I need to replace the last line with

LocalDate date = yearMonth.atDay(1).with(secondTuesday);

Isn't there a cleaner solution that doesn't require the use of atDay(1)?

Solution

  • You have found the best and cleanest (or the least poor) solution yourself already:

    LocalDate date = yearMonth.atDay(1).with(secondTuesday);

    The argument to atDay doesn’t necessarily need to be 1, but it needs to be a valid day of the month in question, so why not 1?

    with() always returns the same type you called it on. That is, YearMonth.with() will always return a YearMonth, never a LocalDate. Therefore you cannot use your adjuster there.

    I understand and share your objection, but what you’ve got already is the best we can do. You can and should probably wrap it inside a method with a nice name.