Java 8 LocalDateTime - 如何在字符串转换中保持 .000 毫秒
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Java 8 LocalDateTime - How to keep .000 milliseconds in String conversion
提问by daniel9x
I have a timestamp that I receive via a Stringin the following format:
我有一个通过String以下格式接收的时间戳：
2016-10-17T12:42:04.000
2016-10-17T12:42:04.000
I am converting it to a LocalDateTimeto add some days to it (then back to a String) via the following line:
我将它转换为 aLocalDateTime以String通过以下行为其添加几天（然后返回到 a ）：
String _120daysLater = LocalDateTime.parse("2016-10-17T12:42:04.000",
DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS")).minusDays(120).toString());
However, I noticed that the response it gives back drops the .000milliseconds.
但是，我注意到它返回的响应减少了.000毫秒。
I'm not sure the cleanest way to ensure that the exact pattern is preserved. For now I'm just adding a single millisecond, and there's probably a way to incorporate the old SimpleDateFormatinto it, but I was hoping there's an even better way.
我不确定确保保留确切模式的最干净方法。现在我只是添加一个毫秒，可能有一种方法可以将旧的SimpleDateFormat合并到其中，但我希望有更好的方法。
回答by Ward
LocalDateTime::toStringomits parts if zero:
LocalDateTime::toString如果为零则省略部分：
The format used will be the shortest that outputs the full value of the time where the omitted parts are implied to be zero.
所使用的格式将是输出完整时间值的最短格式，其中省略部分暗示为零。
Use LocalDateTime::formatinstead of relying on toString().
使用LocalDateTime::format而不是依赖toString().
DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSS");
LocalDateTime _120daysLater = LocalDateTime.parse("2016-10-17T12:42:04.000", formatter).minusDays(120);
// This just uses default formatting logic in toString. Don't rely on it if you want a specific format.
System.out.println(_120daysLater.toString());
// Use a format to use an explicitly defined output format
System.out.println(_120daysLater.format(formatter));
