如何在Java.time中将LocalDateTime的精度设置为纳秒？ [英] How to set precision of LocalDateTime to nanoseconds in Java.time?

问题描述

根据 java.time文档，java.time应该能够以纳秒精度呈现LocalDateTime或LocalTime，但是当我运行 LocalDateTime.now（）并打印出来时，它只显示3数字而不是9。

According to the java.time documentation, java.time should be able to present a LocalDateTime or LocalTime with nanoseconds precision, but when I run LocalDateTime.now() and print out, it only shows 3 digits instead of 9.

喜欢这样：

2016-08-11T22:17:35.031

有没有办法获得更高的精度？

Is there a way to get a higher precision?

推荐答案

我假设您只是使用 LocalDateTime.toString（），在这种情况下< a href =https://docs.oracle.com/javase/8/docs/api/java/time/LocalDateTime.html#toString--\"rel =nofollow>文档上写着：

I am assuming you are just using LocalDateTime.toString(), in which case the documentation reads:

使用的格式是最短的，输出省略的部分隐含为零的时间的全部值。

The format used will be the shortest that outputs the full value of the time where the omitted parts are implied to be zero.

如果你想要额外的数字要显示，即使它们是零，您还需要创建一个 DateTimeFormatter 并改为使用：

If you want additional digits to show up, even if they are zeroes, you will need to create a DateTimeFormatter and use that instead:

DateTimeFormatter formatter =
    DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss.SSSSSSSSS");

System.out.println(LocalDateTime.now().format(formatter));

此外， LocalDateTime.now（）使用系统默认 时钟 仅保证具有毫秒精度，但如果可用，则可以使用更高分辨率的时钟。您的平台可能没有可用于JRE的时钟，其分辨率高于毫秒。

Further, LocalDateTime.now() uses the system default Clock which is only guaranteed to have millisecond precision, but can use a higher resolution clock if one is available. It's possible that your platform doesn't have a clock that is available to the JRE with a higher resolution than milliseconds.

更新 - 您可以还可以使用 LocalDateTime.of（）创建 LocalDateTime ，以验证是否存储纳秒并将包含在返回值中默认 LocalDateTime.toString（）方法：

Update - You can also create a LocalDateTime with LocalDateTime.of() to verify that nanoseconds are stored and will be included in the return value of the default LocalDateTime.toString() method:

LocalDateTime when =
    LocalDateTime.of(2016, Month.AUGUST, 12, 9, 38, 12, 123456789);

System.out.println(when);

上述输出为：

2016-08-12T09:38:12.123456789

这篇关于如何在Java.time中将LocalDateTime的精度设置为纳秒？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！