In java Regex, How can I get a certain part of a fileName

Question

I have a String which is basically a file name. I need to retrieve a certain part of the file name. It is the value before second - (dash). Filenames will be in format example:

fileName-014qsqs-xxxxyyyzzz.txt

I need to get as a result:

fileName-014qsqs

How can I use regex to it?

Thanks

So what do you want to extract in your example, `014qsqs`? What did you try so far? And does it have to be a regex or would splitting the filename at dashes be ok as well? — Thomas, May 09 '17 at 11:07
Why do you specifically want to use a regex for this? Regular expressions are not a golden hammer for any task that has to do with strings, and a simple `indexOf` and `substring` will do the job here. — Jesper, May 09 '17 at 11:08
http://stackoverflow.com/questions/3481828/how-to-split-a-string-in-java — user2173372, May 09 '17 at 11:10
No actually I need everything before the second dash. In this case, I need to have as a result "fileName-014qsqs" — ErEcTuS, May 09 '17 at 11:32

Daniel Centore · Answer 1 · 2017-05-09T11:45:04.617

2

When trying to figure this out, it can be helpful to use a regex tester (e.g. http://www.regexplanet.com/advanced/java/index.html)

The regex (.*?-.*?)-.* matches what you are looking for.

.*: Any character any number of times

?: Makes it non-greedy, so it only does as few as possible to match

-: Literal dash

(): The parentheses make it a group so it can be extracted.

The entire program looks like this:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main
{
    public static void main(String atrgs[])
    {
        String line = "fileName-014qsqs-xxxxyyyzzz.txt";
        Pattern pattern = Pattern.compile("(.*?-.*?)-.*");
        Matcher matcher = pattern.matcher(line);
        while (matcher.find()) {
            System.out.println(matcher.group(1));
        }
    }
}

And has the output fileName-014qsqs.

edited May 09 '17 at 11:45

answered May 09 '17 at 11:17

Daniel Centore

3,220
1
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Have you crosschecked this with filenames containing more than 2 dashes? – Sebastian Proske May 09 '17 at 11:29
Thanks this really helps but I need everything before the second "-". In this case it will be "fileName-014qsqs" – ErEcTuS May 09 '17 at 11:31
@SebastianProske No. OP, is supporting >2 dashes req'd? – Daniel Centore May 09 '17 at 11:34
@Daniel Centore, much better, thanks ;-) But what if my file has more than 2 dashes, like : fileName-05-abc-def-zzz-yyy. Here, I only need : fileName-05 – ErEcTuS May 09 '17 at 11:40

score 0 · Answer 2 · answered May 09 '17 at 11:43

You can use this regular expression:

"([^-]*-[^-]*)-.*"

Explanation: any character but "-" is expressed as "[^-]" hence the

([^-]*-[^-]*)

captures a sequence of non-"-" characters separated by a single "-", next a second "-" followed by any further text.

J.Fernandes · Answer 3 · 2017-05-09T13:39:07.200

0

Hi i probably do a while and when find the 2 "-" stop.Sry can't comment

edited May 09 '17 at 13:39

answered May 09 '17 at 11:44

J.Fernandes

87
2
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In java Regex, How can I get a certain part of a fileName

3 Answers3