I have the following Java regex, which I didn’t write and I am trying to modify:
^class-map(?:(\\s+match-all)|(\\s+match-any))?(\\s+[\\x21-\\x7e]{1,40})$
^ ^
It’s similar to this one.
Note the first question mark. Does it mean that the group is optional? There is already a question mark after the corresponding ). Does the colon have a special meaning in regex?
The regex compiles fine, and there are already JUnit tests that show how it works. It’s just that I’m a bit confused about why the first question mark and colon are there.
(?:starts a non-capturing group. It’s no different to(unless you’re retrieving groups from the regex after use. See What is a non-capturing group? What does a question mark followed by a colon (?:) mean?.