Parsing an ISO 8601 date in Java8 when all fields (including separators, but not including years) are optional

Question

I have a requirement for parsing ISO8601 formatted strings in Java with various levels of accuracy. Some examples of the string I need to parse are:

• 2018

Answer 1

You can create a DateTimeFormatter with DateTimeFormatterBuilder, which has a method called parseDefaulting(). parseDefaulting() could set the default value if there is no matching.