Get substring between 3rd colon and 4th colon

Question

I have strings in the below pattern:

ab:ab:ab:1:ab
ac:ac:ac:2:ac
ad:ad:ad:3:ad

I have to extract the string between the 3rd colon and the 4th colon.

For the above example strings, the results would be "1", "2" and "3".

What is a short way in Java using string functions to extract it?

See https://stackoverflow.com/questions/504103/how-do-i-write-a-correct-micro-benchmark-in-java/4480774#4480774 — tgdavies, Oct 29 '22 at 01:26
Just any piece of code that works. I meant shorter rather than efficient. — AutoTester999, Oct 29 '22 at 01:28
Just use `split`. Which is neither time nor space efficient, as it uses a regex and makes copies of parts of the string you con't care about. — tgdavies, Oct 29 '22 at 01:32
Your examples all have the part you want to extract in position 9. Is that always going to be the case? Or will it vary? `abcd:e:fghijk:123:trwe` for example? — Old Dog Programmer, Oct 29 '22 at 01:46
"What is a short way in Java using string functions to extract it?" - The call to a dedicated method. I mean, if the correct abstraction of your requirement is indeed "extract the string between the 3rd colon and the 4th colon", and you want to write fast efficient code, it's gonna be a few lines in said method. — Dreamspace President, Oct 29 '22 at 05:12

score 2 · Accepted Answer · edited Oct 29 '22 at 07:37

2

You can just split by ":" and get the fourth element:

something like:

Stream.of("ab:ab:ab:1:ab", "ac:ac:ac:2:ac", "ad:ad:ad:3:ad")
      .map(s -> s.split(":")[3])
      .forEach(System.out::println);

Output:

1
2
3

edited Oct 29 '22 at 07:37

Basil Bourque

303,325
100
852
1,154

answered Oct 29 '22 at 01:39

Teddy Tsai

414
1
13

Note to readers: To collect results, replace `.forEach` with `.toList`. – Basil Bourque Oct 29 '22 at 07:39

score 1 · Answer 2 · answered Oct 29 '22 at 04:05

And as an alternative, replace the entire string with the desired item via a capture.

(?:.*?:){3} - non capturing group of three reluctant strings followed by a :
(.*?) - the capture of the target between 3rd and 4th colon.
.*$ - the rest of the string to the end.
$1 - the reference to the first (and only) capture group

String[] data = { "ab:ab:ab:1:ab",
 "ac:ac:ac:2:ac",
 "ad:ad:ad:3:ad"};

for (String str : data) {
    System.out.println(str.replaceAll("(?:.*?:){3}(.*?):.*$","$1"));
}

prints

1
2
3

Get substring between 3rd colon and 4th colon

2 Answers2