如何将日期转换为毫秒 [英] How to convert a date to milliseconds

问题描述

我想将 String myDate =2014/10/29 18:10:45转换为
long ms（即currentinmlilies）？我在Google上查找，但我只能找到如何将 ms 转换为 date 。

I want to convert String myDate = "2014/10/29 18:10:45" to long ms (i.e. currentinmlilies)? I look for it on Google, but I can only find how to convert ms to date.

注意：为了说清楚，我想从1970/1/1格式的日期获得ms。

Note: To make it clear, I want to get the ms from the date in 1970/1/1 format.

推荐答案

你没有日期，你有字符串表示日期。您应该将 String 转换为 Date ，然后获取毫秒数。要将字符串转换为日期，反之亦然，您应该使用 SimpleDateFormat class。

You don't have a Date, you have a String representation of a date. You should convert the String into a Date and then obtain the milliseconds. To convert a String into a Date and vice versa you should use SimpleDateFormat class.

以下是您想要/需要做的示例（假设此处不涉及时区）：

Here's an example of what you want/need to do (assuming time zone is not involved here):

String myDate = "2014/10/29 18:10:45";
SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss");
Date date = sdf.parse(myDate);
long millis = date.getTime();

但是，要小心，因为在Java中，获得的毫秒数是所需时期与1970-01之间的毫秒数-01 00:00:00。

Still, be careful because in Java the milliseconds obtained are the milliseconds between the desired epoch and 1970-01-01 00:00:00.

使用自Java 8以来可用的新日期/时间API：

Using the new Date/Time API available since Java 8:

String myDate = "2014/10/29 18:10:45";
LocalDateTime localDateTime = LocalDateTime.parse(myDate,
    DateTimeFormatter.ofPattern("yyyy/MM/dd HH:mm:ss") );
/*
  With this new Date/Time API, when using a date, you need to
  specify the Zone where the date/time will be used. For your case,
  seems that you want/need to use the default zone of your system.
  Check which zone you need to use for specific behaviour e.g.
  CET or America/Lima
*/
long millis = localDateTime
    .atZone(ZoneId.systemDefault())
    .toInstant().toEpochMilli();

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