javaregexjava-8java-21

Strange Java regex matching behavior regarding negation via ^

In Java 8, the following script prints true

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

public class Main {
    public static void main(String[] args) {
        String regex = "^(/[^/[a-zA-Z0-9_.-]+]*)+/?$";
        String inString = "/tmp"; // the same goes for e.g. /usr/pgsql-15
        
        Matcher matcher = Pattern.compile(regex).matcher(inString);

        System.out.println("Matches regex: " + matcher.matches());
    }
}

In Java 21, however, it prints false. Why? Could this be related to JDK-6609854?

Solution

  • It turns out that this is a bug from Java 8 (link). Also see this mailing discussion.

    The solution is to update the regex, for example:

    ^(/[-a-zA-Z0-9_.]+)+/?$