Java / Android regex question

Question

I would like to create a regex in Java / Android which truncates a string after, or actually at, the third comma. Is this possible? Any suggestions to get me started on this?

Suggestions to get you started on this? Learn regular expressions. — R. Martinho Fernandes
– R. Martinho Fernandes, Commented May 30, 2011 at 18:36
@Martihno - I know...I know. I just do them infrequently enough that I always kind of start from scratch. Posting a question on SO gives me a bit of motivation to get going on it. — Jack BeNimble
– Jack BeNimble, Commented May 30, 2011 at 19:05

Community · Accepted Answer · 2017-05-23 12:04:19Z

4

Not sure regular expressions would be my first approach here. Below are my alternatives anyway.

Using regular expressions (ideone.com demo)

Matcher m = Pattern.compile("(.*?,.*?,.*?),").matcher(str);
if (m.find())
    str = m.group(1);

Using indexOf / substring (ideone.com demo)

str = str.substring(0, str.indexOf(',',
                       str.indexOf(',',
                       str.indexOf(',') + 1) + 1));

Using nthOccurrence (ideone.com demo)

str = str.substring(0, nthOccurrence(str, ',', 2));

edited May 23, 2017 at 12:04

CommunityBot

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answered May 30, 2011 at 18:41

aioobe

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dertkw · Accepted Answer · 2011-05-30 18:41:04Z

3

Take a look at Pattern class.

Alternatives: String#split your string or use a StringTokenizer.

answered May 30, 2011 at 18:41

dertkw

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4 Comments

aioobe Over a year ago

Using split or StringTokenizer would force him to concatenate the results. Not very elegant imo.

dertkw Over a year ago

Sure, but I don't know what he actually wants to achieve or do with the result (thus only 'alternatives'). Just wanted give some suggestions as stated in his answer ;)

Jack BeNimble Over a year ago

Thanks for the idea. All the answers were great, but since regular expressions look like swears to me, I went with a nice little split and a loop. .

aioobe Over a year ago

Did you look at my two non-regex solutions? They don't require any loops.

Jeremy W. Sherman · Accepted Answer · 2011-05-30 18:42:32Z

1

Translate s/([^,]*,){3}.+/\1/ into Java regex-ese to truncate after the third comma, s/([^,]*,[^,]*,[^,]*),.+/\1/ to have the truncated portion include the third comma.

answered May 30, 2011 at 18:42

Jeremy W. Sherman

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Comments

Ted Hopp · Accepted Answer · 2011-05-30 18:52:29Z

1

int comma = -1;
int n = 0;
do {
    comma = str.indexOf(',', comma + 1);
} while (comma >= 0 && ++n < 3);
if (comma > 0) {
    str = str.substring(0, comma);
} else {
    // third comma not found
}

answered May 30, 2011 at 18:52

Ted Hopp

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