DateTimeFormater with optional section

问题

I'm writing an application to manipulate text data, Which will change the content of input string and create new output String based on the format of input string.

I encounter some problem with recognized the date time string. Based on the document the input date time may have some optional section, here the sample pattern:

yyyy[MM[dd[HHmm]]][Z]

So after some digging on the web, my first attempt to use the parseBest function.

public boolean checkFormatDate(string input){
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy[MM[dd[HHmm]]][Z]");
    try {
        TemporalAccessor temporalAccessor = formatter.parseBest(input, ZonedDateTime::from, LocalDateTime::from, LocalDate::from);
        return true;
    } catch (Exception e) {
        return false;
    }
}

But the code above failed with these case:

1900 190001 190001011440

My suspect is that the queries that parse the parseBest method is not correct. Can someone help me with this.

Edit:

Here is the exception log:

java.time.format.DateTimeParseException: Text '190001011440' could not be parsed at index 0 at java.time.format.DateTimeFormatter.parseResolved0(DateTimeFormatter.java:1947) at java.time.format.DateTimeFormatter.parseBest(DateTimeFormatter.java:1895)

回答1:

The problem seems to be the pattern yyyy, which is creating a formatter as follows (System.out.println(formatter)):

Value(YearOfEra,4,19,EXCEEDS_PAD)[Value(MonthOfYear,2)[Value(DayOfMonth,2)[Value(HourOfDay,2)Value(MinuteOfHour,2)]]][Offset(+HHMM,'+0000')]

Note the 4,19 in the first part - minimum width of 4 and max of 19. Build the formatter as follows and it should work:

    DateTimeFormatterBuilder b = new DateTimeFormatterBuilder();
    formatter = b.appendValue(ChronoField.YEAR_OF_ERA, 4, 4, SignStyle.EXCEEDS_PAD).appendPattern("[MM[dd[HHmm]]][Z]").toFormatter();

来源：https://stackoverflow.com/questions/31645243/datetimeformater-with-optional-section

标签

java

datetime-format