I have a user input field and would like to parse his date, whatever he puts in.
The user might provide his date with a leading zero or without one, so I wanna be able to parse an input like this
02.05.2019
and also this
2.5.2019
But as far as I can tell there is no way to make the leading zero optional, either always have 2 digits like 01, 03, 12 and so on, or only have the necessary digits like 1, 3, 12.
So apparently I have to decide whether to allow leading zeros or not, but is there seriously no way to make the leading zero optional ?
Well, I tested a pattern that included a leading zero dd.MM.uuuu and I tested a pattern that did not include a leading zero d.M.uuuu and when I parsed the wrong input with the wrong pattern exceptions were thrown.
Therefore my question is if there is a way to make the leading zero optional.
This is trivial when you know it. One pattern letter, for example d or M, will accept either one or two digits (or for year up to 9 digits).
DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("d.M.u");
System.out.println(LocalDate.parse("02.05.2019", dateFormatter));
System.out.println(LocalDate.parse("3.5.2019", dateFormatter));
System.out.println(LocalDate.parse("4.05.2019", dateFormatter));
System.out.println(LocalDate.parse("06.5.2019", dateFormatter));
System.out.println(LocalDate.parse("15.12.2019", dateFormatter));
Output:
2019-05-02 2019-05-03 2019-05-04 2019-05-06 2019-12-15
I searched for this information in the documentation and didn’t find it readily. I don’t think it is well documented.