java.time.LocalDate 范围内的生日

Question

I'm trying to select birthdays (independent of the year) within a Collection of java.time.LocalDate . Why LocalDate ? because this type seems the best for birthday.

Let's say I want to filter the birthdays between March 6 and April 30 irrespective of the year. How to do this ?

If I were to do it, I would replace the year in LocalDate and use the method isAfter and isBefore . The fact that I have to change the year is just a plain hack. Or I used the wrong data type (LocalDate)

Answer 1

I would rather use the type MonthDay which is the "date-without-year" and which is also comparable and offers methods like isAfter() or isBefore() . Furthermore, a MonthDay can be extended to a LocalDate using the method atYear(int) .

If you insist on LocalDate then you should only use leap years because otherwise the 29th of February would be a problem.

Answer 2

List<LocalDate> birthdays = Arrays.asList(
        LocalDate.of(1990, Month.JANUARY, 5),
        LocalDate.of(1992, Month.MARCH, 7),
        LocalDate.of(1995, Month.MAY, 5));
MonthDay filterFrom = MonthDay.of(Month.MARCH, 6);
MonthDay filterTo = MonthDay.of(Month.APRIL, 30);

List<LocalDate> filteredDates = birthdays.stream()
        .filter(date -> {
            MonthDay md = MonthDay.from(date);
            return md.compareTo(filterFrom) >= 0 && md.compareTo(filterTo) <= 0;
        })
        .collect(Collectors.toList());

System.out.println(filteredDates);