将java.time转换为Calendar

Question

从java.time.Instant或java.time.ZonedDateTime获取Calendar对象的最简单方法是什么？

Answer 1

Getting a Calendar instant from ZonedDateTime is pretty straight-forward, provided you know that there exists a GregorianCalendar#from(ZonedDateTime) method. There was a discussion in Threeten-dev mail group , about why that method is not in Calendar class. Not a very deep discussion though.

However, there is no direct way to convert from an Instant to Calendar . You've to have an intermediate state for that:

Instant instant = Instant.now();
ZonedDateTime zdt = ZonedDateTime.ofInstant(instant, ZoneId.systemDefault());
Calendar cal1 = GregorianCalendar.from(zdt);

This is probably because, as evident from the table on this oracle tutorial , an Instant maps to Date rather than a Calendar . Similarly, a ZonedDateTime maps to a Calendar .

Answer 2

您需要使用瞬间获取TimeZone，然后您才能获得日历。

Calendar myCalendar = GregorianCalendar.from(ZonedDateTime.ofInstant(Instant.now(), ZoneId.systemDefault()));

Answer 3

GregorianCalendar.from(ZonedDateTime.ofInstant(instant, zoneId))怎么样？