Java calculate days in year, or between two dates

Question

Is there a method in any native Java class to calculate how many days were/will be in a specific year? As in, was it a Leap year (366 days) or a normal year (365 days)?

Answer 1

since JAVA 8

Days in a year:

LocalDate d = LocalDate.parse("2020-12-31");                   // import java.time.LocalDate;
return d.lengthOfYear();                                       // 366

Days to my birthday:

LocalDate birth = LocalDate.parse("2000-02-29");
LocalDate today = LocalDate.now();                             // or pass a timezone as the parameter

LocalDate thisYearBirthday = birth.withYear(today.getYear());  // it gives Feb 28 if the birth was on Feb 29, but the year is not leap.
LocalDate nextBirthday = today.isAfter(thisYearBirthday)
    ? birth.withYear(today.getYear() + 1)
    : thisYearBirthday;

return DAYS.between(today, nextBirthday);                      // import static java.time.temporal.ChronoUnit.DAYS;