Java计算一年中的天数，或两个日期之间的天数
问题描述：
在任何本机Java类中是否都存在一种方法来计算特定年份中的多少天/将要多少天?就像是 Le年(366天)还是正常年份(365天)?
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)?
还是我需要自己写?
我正在计算两个日期之间的天数，例如，到我生日还剩多少天.我要考虑到year年2月29日.除了29号，我都做完了.
I'm calculating the number of days between two dates, for example, how many days left until my birthday. I want to take into account the February 29 of Leap year. I have it all done except that 29th.
答
自 JAVA 8
一年中的天数:
since JAVA 8
Days in a year:
LocalDate d = LocalDate.parse("2020-12-31"); // import java.time.LocalDate;
return d.lengthOfYear(); // 366
我生日的天数:
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;