将java.time转换为Calendar [英] Converting java.time to Calendar

问题描述

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

What is the simplest way of getting a Calendar object from a java.time.Instant or java.time.ZonedDateTime?

推荐答案

如果您知道存在 Threeten-dev邮件组，说明为什么该方法不在Calendar类中.不过，讨论不是很深入.

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.

但是，没有直接的方法可以将Instant转换为Calendar.您必须为此设置一个中间状态:

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);

这可能是因为，从此oracle教程的表中可以明显看出，Instant映射到Date而不是Calendar.同样，ZonedDateTime映射到Calendar.

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.

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