Java Regex: Matching a string between 2 colons

Question

I'm trying to write a Java regex that will find all the strings between 2 :. If the string between the characters has whitespaces, line endings or tabs, it should be ignored. Empty strings are also ignored. _ are ok! The group can either include the enclosing : or not.

Here are a few tests and the expected groups:

"test :candidate: test" => ":candidate:"
"test :candidate: test:" => ":candidate:"
"test :candidate:_test:" => ":candidate:", ":_test:"
"test :candidate::test" => ":candidate:"
"test ::candidate: test" => ":candidate:"
"test :candidate_: :candidate: test" => ":candidate_:", ":candidate:"
"test :candidate_:candidate: test" => ":candidate_:", ":candidate:"

I've tested a lot of regex and these ones almost work:

":(\\w+):"
":[^:]+:"

I still have a problem when the 2 groups "share" a colon:

"test :candidate_: :candidate: test" => ":candidate_:", ":candidate:" // OK
"test :candidate_:candidate: test" => ":candidate_:" // ERROR! :(

It seems like the first group "consumes" the second colon and that the matcher can't find the second string I expected.

Can someone point me in the right direction to solve this problem? Can you also elaborate on why the matcher "consumes" the colon?

Thanks.

Answer 1

Use a Positive Lookahead for capturing to get the overlapping matches.

(?=(:\\w+:))

Note: You can access your match result by refering to capturing group #1 ( Live Demo )