Wildcard in DateTimeFormatter

Question

I need to parse a string into a LocalDate. The string looks like 31.* 03 2016 in regex terms (i.e. .* means that there may be 0 or more unknown characters after the day number).

Example input/output: 31xy 03 2016 ==> 2016-03-31

I was hoping to find a wildcard syntax in the DateTimeFormatter documentation to allow a pattern such as:

LocalDate.parse("31xy 03 2016", DateTimeFormatter.ofPattern("dd[.*] MM yyyy"));

but I could not find anything.

Is there a simple way to express optional unknown characters with a DateTimeFormatter?

ps: I can obviously modify the string before parsing it but that's not what I'm asking for.

Answer 1

I’d do it in two steps, use a regexp to get the original string into something that LocalDate can parse, for example:

String dateSource = "31xy 03 2016";
String normalizedDate = dateSource.replaceFirst("^(\\d+).*? (\\d+ \\d+)", "$1 $2");
LocalDate date = LocalDate.parse(normalizedDate, DateTimeFormatter.ofPattern("dd MM yyyy"));
System.out.println(date);

I know it’s not what you asked for.