Java 8 LocalDateTime有不同的结果 [英] Java 8 LocalDateTime has different results
问题描述
我正在尝试更新一些代码以使用Java 8的功能来解析多种日期格式.我在盒子上的本地时间设置为 UTC-11 .
I am trying to update some code to use Java 8's feature for parsing multiple date formats. my local time on my box is set to UTC-11.
下面的代码在使用SimpleDateformat时起作用.
the below code works when using the SimpleDateformat.
DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSXXX");
Date correctDate = dateFormat.parse("2018-09-6T03:28:59.039-04:00");
//Gives me correct date
System.println( correctDate);//Wed Sep 5th 20:28:59 GMT-11:00 2018
我正在尝试使用Java 8中的DateTimeFormatter更新此代码以提供与上述相同的日期，以便我可以处理其他日期格式..
I am trying to update this code to give the same date as above with the DateTimeFormatter in Java 8 , so i can handle another date format..
DateTimeFormattter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss[.SSS]XXX");
LocalDateTime updateDate = LocalDateTime.parse( "2018-09-6T03:28:59.039-04:00", dtf);
//shows the wrong date of 2018-09-06 03:28:59.039.
System.out.println( updateDate.toString() );// 2018-09-06 03:28:59.039
[已解决] 我可以通过使用ZonedDateTime来解决此问题.
[solved] I was able to fix this by using ZonedDateTime.
ZonedDateTime zdt = ZonedDateTime.parse("2018-09-6T03:28:59.039-04:00");
zonedDateTime = zdt.withZoneSameInstance(ZoneId.of("GMT"));
Date correctDate = Date.from( zonedDateTime.toInstance());
//correctDate是我想要的2018年9月5日星期三20:28:59 GMT-11:00
//correctDate is what i wanted Wed Sep 5th 20:28:59 GMT-11:00 2018
推荐答案
将日期字符串解析为LocalDateTime后，区域偏移就会丢失，因为LocalDateTime不包含任何时区或偏移信息.
再次将LocalDateTime格式化为字符串时，解析后的时间将没有偏移.
As soon as you parse your date string into a LocalDateTime the zone offset is lost because LocalDateTime does not hold any time zone or offset information.
When you format the LocalDateTime to a string again, you'll only have the time as it was parsed without offset.
The Documentation of LocalDateTime clearly explains this:
此类不存储或表示时区.相反，它是对用于生日的日期的描述，以及在墙上时钟上看到的本地时间.如果没有其他信息(例如偏移量或时区)，则无法在时间轴上表示时刻.
This class does not store or represent a time-zone. Instead, it is a description of the date, as used for birthdays, combined with the local time as seen on a wall clock. It cannot represent an instant on the time-line without additional information such as an offset or time-zone.
您应该考虑使用OffsetDateTime或ZonedDateTime.
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