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

create a lookup table of DateFormatters or whatever you're using based on the length of the input String and the occurrence of 'T'