How to create DateTimeformatter with optional seconds arguments

Question

I am trying to create a DateTimeformatter to validate following date times:

String date1 = \"2017-07-06T17:25:28\";
String date2 = \"2017-07-06T         


        

Answer 1

Try set minWidth to 1, i.e. .appendFraction(ChronoField.MICRO_OF_SECOND, 1, 6, true).

Answer 2

You must create an optional section (using optionalStart() and optionalEnd() methods) containing the decimal point followed by 1 to 6 digits:

String DATE_TIME_FORMAT_PATTERN = "yyyy-MM-dd'T'HH:mm:ss";
DateTimeFormatter formatter1 = new DateTimeFormatterBuilder()
    .appendPattern(DATE_TIME_FORMAT_PATTERN)
    // optional decimal point followed by 1 to 6 digits
    .optionalStart()
    .appendPattern(".")
    .appendFraction(ChronoField.MICRO_OF_SECOND, 1, 6, false)
    .optionalEnd()
    .toFormatter();

This parses from date1 to date7 and throws a java.time.format.DateTimeParseException with date8.

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This also works the same way:

String DATE_TIME_FORMAT_PATTERN = "yyyy-MM-dd'T'HH:mm:ss";
DateTimeFormatter formatter1 = new DateTimeFormatterBuilder()
    .appendPattern(DATE_TIME_FORMAT_PATTERN)
    // optional decimal point followed by 1 to 6 digits
    .optionalStart()
    .appendFraction(ChronoField.MICRO_OF_SECOND, 1, 6, true)
    .optionalEnd()
    .toFormatter();