The start() method of Matcher Class is used to get the start index of the match result already done.
Syntax:
public int start()
Parameters: This method do not takes any parameter.
Return Value: This method returns the index of the first character matched.0
Exception: This method throws IllegalStateException if no match has yet been attempted, or if the previous match operation failed.
Below examples illustrate the Matcher.start() method:
Example 1:
// Java code to illustrate start() method import java.util.regex.*; public class GFG { public static void main(String[] args) { // Get the regex to be checked String regex = "(G*k)"; // Create a pattern from regex Pattern pattern = Pattern.compile(regex); // Get the String to be matched String stringToBeMatched = "Geeks"; // 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[pattern=(G*k) region=0,5 lastmatch=]
3
Example 2:
// Java code to illustrate start() method 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[pattern=(G*G) region=0,3 lastmatch=]
0
2
Reference: Oracle Doc