What does the regular expression [.\d\D]* mean?

Question

What does [.\\d\\D]* mean.

I am trying to check a valid java main method statement by

java.matches("[.\\d\\D]*((public)\\s(static)\\s(void)\\s(main)\\((String)\\[\\]\\s(args)\\))[.\\d\\D]*");

what does that part mean?

You can http://regexpal.com/ it is really helpful – Noam Rathaus Nov 24 '13 at 07:16 — Noam Rathaus, Nov 24 '13 at 07:16
regex101.com is also useful. – gatsbyz Jun 22 '18 at 21:00 — gatsbyz, Jun 22 '18 at 21:00

score 4 · Accepted Answer · answered Nov 24 '13 at 07:14

4

Well [.\d\D]* means match:

0 or more of anyone of these properties

IMO this is not really required since this can effectively match anything and is equivalent of .* with DOTALL switch.

answered Nov 24 '13 at 07:14

anubhava

does .* also include the new line (\n)? One of my test cases ("\n // ///*\"public static void main(String[] args)\"*/ \n ") is failing. – gatsbyz Nov 24 '13 at 07:18
It is indeed odd. Even without DOTALL, `[\d\D]`, `[\s\S]`, or `[\w\W]` (i.e. no `.`) are the forms I've seen. The extra `.` makes it look like the original author just started throwing things together at random. – user2864740 Nov 24 '13 at 07:18
@SWKING It's odd because the `.` means nothing there (as it is covered by `[\d\D]`). Anyway, see DOTALL: http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html#DOTALL – user2864740 Nov 24 '13 at 07:20
DOT will not match newline unless you use `(?s)` in front of your regex like `"a\nb".matches("(?s).*");` OR `Pattern.DOTALL` flag – anubhava Nov 24 '13 at 07:21

1 Answers1