java.time.DateTimeFormatter : Need ISO_INSTANT that always renders milliseconds

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逝去的感伤
逝去的感伤 2021-02-07 03:55

I\'m trying to cleanup a mix of various code around datetime management to only Java 8 java.time namespace. Right now I have a small issue with the default DateTimeFormatter for

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  •  醉梦人生
    2021-02-07 04:37

    The accepted Answer by Florent is correct and good.

    I just want to add some clarification.

    The mentioned formatter, DateTimeFormatter.ISO_INSTANT, is default only for the Instant class. Other classes such as OffsetDateTime and ZonedDateTime may use other formatters by default.

    The java.time classes offer a resolution up to nanosecond, much finer granularity than milliseconds. That means up to 9 digits in the decimal fraction rather than merely 3 digits.

    The behavior of DateTimeFormatter.ISO_INSTANT varies by the number of digits in the decimal fraction. As the doc says (emphasis mine):

    When formatting, the second-of-minute is always output. The nano-of-second outputs zero, three, six or nine digits as necessary.

    So depending on the data value contained within the Instant object, you may see any of these outputs:

    2011-12-03T10:15:30Z

    2011-12-03T10:15:30.100Z

    2011-12-03T10:15:30.120Z

    2011-12-03T10:15:30.123Z

    2011-12-03T10:15:30.123400Z

    2011-12-03T10:15:30.123456Z

    2011-12-03T10:15:30.123456780Z

    2011-12-03T10:15:30.123456789Z

    The Instant class is meant to be the basic building block of java.time. Use it frequently for data passing, data storage, and data exchange. When generating String representations of the data for presentation to users, use OffsetDateTime or ZonedDateTime.

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