Matcher start() method in Java with Examples

Last Updated : 3 Jul, 2026

The start() method of the Matcher class is used to return the starting index of the most recent match found by the find() method. It helps identify the exact position where a matching pattern begins in the input string.

  • Must be called after a successful find() or matches() operation.
  • Returns an integer representing the first character's index.
  • Throws IllegalStateException if no successful match exists.
Java 
import java.util.regex.*;

public class Main {
    public static void main(String[] args) {

        Pattern pattern = Pattern.compile("Java");
        Matcher matcher = pattern.matcher("Learn Java Programming");

        if (matcher.find()) {
            System.out.println("Start Index: " + matcher.start());
        }
    }
}

Output
Start Index: 6

Explanation: The word "Java" starts at index 6 in the string "Learn Java Programming", so start() returns 6.

Syntax

public int start()

Returns

  • An integer representing the starting index of the matched substring.

Exception

  • IllegalStateException: Thrown if no match has been attempted or the previous match failed.

Example 1: Java code to illustrate start() method

Java 
import java.util.regex.*;

public class GFG {
    public static void main(String[] args) {

        // Regex pattern
        String regex = "(G*k)";

        // Create Pattern object
        Pattern pattern = Pattern.compile(regex);

        // Input string
        String stringToBeMatched = "Geeks";

        // Create Matcher object
        Matcher matcher = pattern.matcher(stringToBeMatched);

        // Find matches and print starting index
        while (matcher.find()) {
            System.out.println("Matched Text: " + matcher.group());
            System.out.println("Start Index: " + matcher.start());
        }
    }
}

Output
Matched Text: k
Start Index: 3

Explanation: In this example, the regex (G*k) matches the character k in the string "Geeks". The find() method locates the match, and start() returns its starting index, which is 3.

Example 2:

Java 
import java.util.regex.*;

public class GFG {
    public static void main(String[] args)
    {

        // Get the regex to be checked
        String regex = "(G*G)";

        // Create a pattern from regex
        Pattern pattern
            = Pattern.compile(regex);

        // Get the String to be matched
        String stringToBeMatched = "GFG";

        // Create a matcher for the input String
        Matcher matcher
            = pattern
                  .matcher(stringToBeMatched);

        // Get the current matcher state
        MatchResult result
            = matcher.toMatchResult();
        System.out.println("Current Matcher: "
                           + result);

        while (matcher.find()) {
            // Get the first index of match result
            System.out.println(matcher.start());
        }
    }
}

Output
Current Matcher: java.util.regex.Matcher$ImmutableMatchResult@1dbd16a6
0
2

Explanation: The pattern (G*G) matches the character 'G' at two positions in the string "GFG". The first match starts at index 0, and the second match starts at index 2, so start() returns 0 and 2.

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