Java: Regular Expression not matching?

Question

I am trying to extract a special sequence out of a String using the following Regular Expression:

[(].*[)]

My Pattern should only match if the String contains () with text between them.

Somehow, i I create a new Pattern using Pattern#compile(myString) and then match the String using Matcher matcher = myPattern.matcher(); it doesn't find anything, even though I tried it on regexr.com and it worked there.

My Pattern is a static final Pattern object in another class (I directly used Pattern#compile(myString).

Example String to match:

save (xxx,yyy)

What does doesn't find anything mean? - Are you using matches() or find() ? — Alexander
– Alexander, Commented Sep 21, 2016 at 10:21
Also can you mention if you are using matches() or find() — TheLostMind
– TheLostMind, Commented Sep 21, 2016 at 10:24
Okay guys, was my fault, I fixed it as I literally forgot to use find() Thanks for your help! — Adrian K.
– Adrian K., Commented Sep 21, 2016 at 10:27

Community · Accepted Answer · 2017-05-23 10:32:37Z

1

The likely problem here is your quantifier.

Since you're using greedy * with a combination of . for any character, your match will not delimit correctly as . will also match closing ).

Try using reluctant [(].*?[)].

See quantifiers in docs.

You can also escape parenthesis instead of using custom character classes, like so: \\( and \\), but that has nothing to do with your issue.

Also note (thanks esprittn)

The * quantifier will match 0+ characters, so if you want to restrict your matches to non-empty parenthesis, use .+? instead - that'll guarantee at least one character inside your parenthesis.

edited May 23, 2017 at 10:32

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answered Sep 21, 2016 at 10:18

Mena

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1 Comment

JHDev Over a year ago

with [(].*?[)], empty parenthesis like () will be matched so replace * with +

Akhil Job · Accepted Answer · 2016-09-21 10:29:49Z

0

Hope the below code helps : its extracts the data between '(' & ')' including them .

String pattern = "\\(.*\\)";
    String line = "save(xx,yy)";
    Pattern TokenPattern = Pattern.compile(pattern);

    Matcher m = TokenPattern.matcher(line);
    while (m.find()) {

        int start = m.start(0);
        int end = m.end(0);

        System.out.println(line.substring(start, end));

    }

to remove the brackets change 'start' to 'start+1' and 'end' to 'end-1' to change the bounding indexes of the sub-string being taken.

answered Sep 21, 2016 at 10:29

Akhil Job

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