Java Requires Chilkat v11.1.0+

Regular Expression with Capture Groups

See more Regular Expressions Examples

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

Demonstrates the following PCRE2 regular expression:

See the sample code below.

Name:\s+(\w+)\s+(\w+),\s+Email:\s+(\S+)

And apply it to this string:

Name: John Smith, Email: john.smith@example.com

---

Regex Components Explained

Part	Meaning	Matched Text
"Name:"	Matches the literal text "Name:"	"Name:"
"\s+"	Matches one or more whitespace characters (spaces, tabs, etc.)	(space)
"(\w+)"	Capture Group 1: One or more word characters ("a-zA-Z0-9_")	"John"
"\s+"	More whitespace	(space)
"(\w+)"	Capture Group 2: Another word (the last name)	"Smith"
","	A literal comma	","
"\s+"	Whitespace again	(space)
"Email:"	Matches the literal "Email:"	"Email:"
"\s+"	Whitespace	(space)
"(\S+)"	Capture Group 3: One or more non-whitespace characters	"john.smith@example.com"

---

Matches for Your Example String

String:

"Name: John Smith, Email: john.smith@example.com"

Regex Match Groups:

Group	Captured Value
Group 1	"John"
Group 2	"Smith"
Group 3	"john.smith@example.com"

---

Notes on Character Classes

• \w matches [a-zA-Z0-9_] — so it doesn’t include punctuation like a period.
• \S matches any non-whitespace character, so it’s good for capturing an email.

Chilkat2 Java

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

public class ChilkatExample {

    public static void main(String[] args) {
        String subject = "Name: John Smith, Email: john.smith@example.com";
        String pattern = "Name:\\s+(\\w+)\\s+(\\w+),\\s+Email:\\s+(\\S+)";

        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());

        // This is the JSON with the match information.
        // See the JSON parsing code below to get the matched capture group values.

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

        // {
        //   "match": [
        //     {
        //       "group": [
        //         {
        //           "cap": "Name: John Smith, Email: john.smith@example.com",
        //           "idx": 0,
        //           "len": 47
        //         },
        //         {
        //           "cap": "John",
        //           "idx": 6,
        //           "len": 4
        //         },
        //         {
        //           "cap": "Smith",
        //           "idx": 11,
        //           "len": 5
        //         },
        //         {
        //           "cap": "john.smith@example.com",
        //           "idx": 25,
        //           "len": 22
        //         }
        //       ]
        //     }
        //   ]
        // }

        String cap = "";
        int i = 0;
        int matchCount = json.sizeOfArray("match");
        while (i < matchCount) {
            System.out.println("Match " + (i + 1) + ":");
            json.setI(i);
            int j = 0;
            int numCaptureGroups = json.sizeOfArray("match[i].group");
            while (j < numCaptureGroups) {
                json.setJ(j);
                cap = json.stringOf("match[i].group[j].cap");
                System.out.println(j + ": " + cap);
                j = j + 1;
            }

            i = i + 1;
        }

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

        // Output

        // Match 1:
        // 0: Name: John Smith, Email: john.smith@example.com
        // 1: John
        // 2: Smith
        // 3: john.smith@example.com
    }
}