Java Regex: Text extraction into an array list

Issue

I'm struggling with a simple regex, for which I can't seem to get right.

I have some text like so:

This comment is great **[@madeUpUser1](/madeUpUser1)** You said something similar did you mate? **[@madeUpUser2](/madeUpUser2)**

What I would like to end up with is an array list containing the usernames inbetween the parentheses i.e.:

0.madeUpUser1
1.madeUpUser2

And here is the code I have so far:

List<String> matches = Pattern.compile("\\((.+?)\\)")
        .matcher("This comment is great **[@madeUpUser1](/madeUpUser1)** You said something similar did you mate? **[@madeUpUser2](/madeUpUser2)**")
        .results()
        .map(MatchResult::group)
        .collect(Collectors.toList());

However what I'm getting back is this:

0."(/madeUpUser1)"
1."(/madeUpUser2)"

Again, where I want:

0.madeUpUser1
1.madeUpUser2

i.e. without the parentheses and without the forwardslash

Can anyone shed any light on what I'm doing wrong with my regex please?

Solution

Try this regex:

(?<=\\(/)[^)]+(?=\\))

Click for Demo

Explanation

• (?<=\\(/) - positive lookbehind to make sure that the current position is preceded by a (/

• [^)]+ - matches 1 or more occurences(as many as possible) of any character that is not a )

• (?=\\)) - positive lookahead to make sure that the current position is followed by a )

With the regex you are using, \\((.+?)\\), the following happens:

• \\( - matches the opening parenthesis (
• (.+?) - matches any character(except a new line character) 1 or more times, as few as possible. This subpattern will keep on expanding the match until it reaches the ). That's why it is matching everything between the parenthesis(even the /)
• \\) - matches the closing parenthesis )

Answered By - Gurmanjot Singh