Java Requires Chilkat v11.1.0+

Regular Expression with Named Capture Groups

See more Regular Expressions Examples

Demonstrates regular expressions with named capture groups.

See the sample code below.

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

In PCRE2, named capture groups allow you to assign a name to a capturing group, making it easier to reference by name instead of number.

Syntax

(?<name>pattern)

or

(?'name'pattern)

Example

(?<first>\w+)\s+(?<last>\w+)

Applied to:

"John Smith"

Produces:

• first: John
• last: Smith

Chilkat2 Java

import com.chilkatsoft.chilkat2.JsonObject;
import com.chilkatsoft.chilkat2.StringBuilder;

public class ChilkatExample {

    public static void main(String[] args) {
        String subject = "John Smith";
        String pattern = "(?<first>\\w+)\\s+(?<last>\\w+)";

        StringBuilder sb = new StringBuilder();
        sb.append(subject);

        JsonObject json = new JsonObject();
        json.setEmitCompact(false);

        int timeoutMs = 2000;
        int numMatches = sb.regexMatch(pattern, json, timeoutMs);
        if (numMatches < 0) {
            // Probably an error in the regular expression.
            // Suggestion: Use AI to help create and/or diagnose regular expressions.
            System.out.println(sb.getLastErrorText());
            return;
        }

        // Examine the matches:
        System.out.println(json.emit());

        // Here is the JSON showing the matches.
        // Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

        // {
        //   "named": {
        //     "first": 1,
        //     "last": 2
        //   },
        //   "match": [
        //     {
        //       "group": [
        //         {
        //           "cap": "John Smith",
        //           "idx": 0,
        //           "len": 10
        //         },
        //         {
        //           "cap": "John",
        //           "idx": 0,
        //           "len": 4
        //         },
        //         {
        //           "cap": "Smith",
        //           "idx": 5,
        //           "len": 5
        //         }
        //       ]
        //     }
        //   ]
        // }

        // The capture group index is obtained by looking up the name in the JSON result.
        // For example:

        json.setI(json.intOf("named.first"));
        System.out.println("first: " + json.stringOf("match[0].group[i].cap"));

        json.setI(json.intOf("named.last"));
        System.out.println("last: " + json.stringOf("match[0].group[i].cap"));

        // Output is:

        // first: John
        // last: Smith
    }
}