Java regular expression replace issue [duplicate]

Question

public class Main {
    /**
     * @param args
     */
    public static void main(String[] args) {
        String url="http://a.b.com/m/test/index";
        System.out.println(url.replaceAll("^.*?((?<!/)(?:/)(?!/))", ""));
    }
}

The system print is: m/test/index. But in my mind it should print is:/m/test/index. Somebody give some reason?

Use URI/URL class to process them. Don't play around with regular expression in such case. — nhahtdh
– nhahtdh, Commented Sep 16, 2015 at 3:13
While your comment is generally true, a) that's not what the question is about, and b) someone has to write those URL processors. See Asimov's short story "Profession". — Mad Physicist
– Mad Physicist, Commented Sep 16, 2015 at 3:17
Again, I don't disagree. This question is about regex, not specifically URL. The "http" in the string is incidental. — Mad Physicist
– Mad Physicist, Commented Sep 16, 2015 at 3:35
(?:/) will matched the / before m,so we should use (?=/) — Kerwin
– Kerwin, Commented Sep 16, 2015 at 3:51

Mad Physicist · Accepted Answer · 2015-09-16 03:15:24Z

2

Your regex reads "As few characters as possible up to and including the first slash that is neither preceded nor followed by a slash". The slash itself is clearly included in the regex. The fact that it is in a non-capturing group does not mean that it is not part of the match.

answered Sep 16, 2015 at 3:15

Mad Physicist

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