Check for nth occurrence of pattern in regular expression in Java

Question

I want to check nth occurrence of a particular pattern in a input string using Java regular expression. Can you please suggest how to do that?

Use Pattern and Matcher. Count the matches and discard all until you reach your target number. — MightyPork, Nov 21 '13 at 20:44
He's looking for a repeating pattern, not a repeating character. — Rafael Winterhalter, Nov 21 '13 at 20:52
What code have you tried? We won't help you if you haven't done any work on your own. — james.garriss, Nov 22 '13 at 19:56
Not enough reputation here to reopen, but even if the question is not much detailed, I believe this question shouldn't be closed: He's specifically asking for regex. Many answers in the linked "duplicate" question doesn't apply to this question. Please think twice before hitting the "close" button. — thermz, Sep 20 '16 at 09:20

score 3 · Accepted Answer · edited Sep 20 '16 at 10:19

3

This should work:

MatchResult findNthOccurance(int n, Pattern p, CharSequence src){
    Matcher m = p.matcher(src);
    for(int i = 0; i<n; i++) m.find();
    return m;
}

Basically, it just calls find repeatedly on a Matcher obtained from the Pattern. Conveniently, a Matcher is also a MatchResult, so I can just return it straight up.

edited Sep 20 '16 at 10:19

thermz

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answered Nov 21 '13 at 20:55

AJMansfield

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score 2 · Answer 2 · answered Nov 21 '13 at 20:49

Well, you could do the following:

(?:[abc].*+){4}([abc])

This would match 4 occurences of either a, b or c followed by anything (non-eagerly matching such that any a, b or c would not be matched by this anything), followed by a b or c in a captured group ($1).

Simply replace [abc] by the pattern you are looking for. Replace the number in curly braces by n - 1.

Check for nth occurrence of pattern in regular expression in Java

2 Answers2