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javajava-8java-timedatetimeformatter

What is the equivalent format string of DateTimeFormatter.ISO_OFFSET_DATE_TIME?

Do we know if there is an equivalent format string that outputs the same result as DateTimeFormatter.ISO_OFFSET_DATE_TIME?

i.e.

ZonedDateTime dateTime = ZonedDateTime.now();
System.out.println(dateTime.format(DateTimeFormatter.ofPattern(pattern)));
System.out.println(dateTime.format(DateTimeFormatter.ISO_OFFSET_DATE_TIME));

would output the same

Solution

  • No, this is not possible

    On request: Yes, we know that there is no equivalent format pattern string of DateTimeFormatter.ISO_OFFSET_DATE_TIME.

    DateTimeFormatter.ISO_OFFSET_DATE_TIME omits the seconds and/or nano of second if they are zero. If the nanos are non-zero “As many digits will be output as required.” There is no pattern letter or combination of pattern letters that will give you the same behaviour.

    Deep inside DateTimeFormatter, ISO_OFFSET_DATE_TIME uses an ISO_LOCAL_TIME, which in turn is defined in this way:

        ISO_LOCAL_TIME = new DateTimeFormatterBuilder()
            .appendValue(HOUR_OF_DAY, 2)
            .appendLiteral(':')
            .appendValue(MINUTE_OF_HOUR, 2)
            .optionalStart()
            .appendLiteral(':')
            .appendValue(SECOND_OF_MINUTE, 2)
            .optionalStart()
            .appendFraction(NANO_OF_SECOND, 0, 9, true)
            .toFormatter(ResolverStyle.STRICT, null);

    Which is the way to obtain the dynamic behaviour: using a DateTimeFormatterBuilder and its optionalStart and appendFraction methods.

    As an aside, you don’t want to copy the behaviour of ISO_OFFSET_DATE_TIME exactly. You will want to use the built-in formatter.