How to create regex expression for 3 links at once-CodePudding

I created regex expression in JAVA for 2 links at once:

Regex: String REGEX_LINK = "https:..downloads.test.test.testagain.tes.test-test.test."

Pattern pattern = Pattern.compile( REGEX_LINK ".[\w*/]*.((\d{2}-\d{2}-)?\d{4}).pdf" );

But I have to create regex expression for 3 links at once and I don't know how to do that, I need help with this:

I have to create one regex expression to extract String from 1 link: "0218", from 2 link: "09-05-2018", from 3 link: "01-01-18"

Maybe someone has a any idea how to do this?

CodePudding user response：

You could match 2 times 2 digits with an optional hyphen, and then optionally 4 or 2 digits preceded by a hyphen.

Note that the pattern by itself does not verify a valid date.

(?<!\d)(\d{2}-?\d{2}(?:-(?:\d{4}|\d{2}))?)\S*\.pdf\b

Explanation

(?<!\d) Negative lookbehind, assert not a digit to the left
( Capture group 1
- \d{2}-?\d{2} Match 2 digits, optional hyphen and 2 digits
- (?:-(?:\d{4}|\d{2}))? Optionally match - and either 4 or 2 digits
) Close group 1
\S* Match optional non whitespace chars
\.pdf\b Match a dot and pdf followed by a word boundary

Or if there can not be any other digits following till the end of the string:

(?<!\d)(\d{2}-?\d{2}(?:-(?:\d{4}|\d{2}))?)[^\d\s]*\.pdf\b