Match the last occurrence of year

Question

I am trying to match the last occurrence of a persons job end year in Java.

June 1995 – June 2003 (8 years 1 month) would return 2003

1989 – June 1995 (6 years) would return 1995

The information is always in this format so I figured if I start from the end of the string and look for the first 4 digits but I not sure how to do this I know \b\d{4}\b matches the first 4 digits but I require the last occurrence of 4 digits.

Define *doesn't quite work.*. What is the problem you're having? — Tunaki, Aug 16 '16 at 08:44
You can match all the 4 digit values with `\b\d{4}\b` and get the last one. Just keep assigning the found values to a String var. — Wiktor Stribiżew, Aug 16 '16 at 08:44

score 2 · Answer 1 · answered Aug 16 '16 at 08:44

2

You can use this negative lookahead regex:

\bd{4}\b(?!.*\b\d{4}\b)

RegEx Demo

This will match 4 digits in a line when it is not followed by another 4 digits surrounded by word boundaries.

(?!.*\b\d{4}\b) is negative lookahead to assert that there is no 4 digit number ahead of current position in a line.

In Java you can use:

String re = "\\bd{4}\\b(?!.*\\b\\d{4}\\b)";

answered Aug 16 '16 at 08:44

anubhava

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I have just run this but this isn't matching my string. Did you use the Pattern and Matcher class ? – NeptuneGamer Aug 16 '16 at 10:49
Yes you will need to use `Pattern` and `Matcher` APIs. You will need to use `matcher.find()` also to get the match. Can you show your code in question – anubhava Aug 16 '16 at 10:53
1

Its ok I fixed it, I had missed something out! – NeptuneGamer Aug 16 '16 at 10:54

score 1 · Accepted Answer · answered Aug 16 '16 at 08:47

1

Match the lot then grab the second year:

[A-Za-z]+\\s\\d{4}\\s–\\s[A-Za-z]+\\s(?<year>\\d{4}).*

Then just get the value with matcher.group("year").

answered Aug 16 '16 at 08:47

Boris the Spider

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score 1 · Answer 3 · answered Aug 16 '16 at 09:30

In order to get the last occurrence of a pattern, just prepend it with a greedy .*. Then to extract the desired pattern either use \K:

.*\K\b\d{4}\b

(not supported in Java, unfortunately), or wrap your pattern in a capture group:

.*(\b\d{4}\b)

and access the group in your code:

String input = "June 1995 – June 2003 (8 years 1 month)";
Pattern pattern = Pattern.compile(".*(\\b\\d{4}\\b)");
Matcher matcher = pattern.matcher(input);
if (matcher.find()) {
    System.out.print(matcher.group(1));
}

Demo: https://ideone.com/cMAvFH

Match the last occurrence of year

3 Answers3