The start(String string) method of Matcher Class is used to get the start index of the match result already done, from the specified string.
Syntax:
public int start(String string)
Parameters: This method takes a parameter string which is the String from which the start index of the matched pattern is required.
Return Value: This method returns the index of the first character matched from the specified string.
Exception: This method throws:
- IllegalStateException if no match has yet been attempted, or if the previous match operation failed.
- IndexOutOfBoundsException if there is no capturing group in the pattern with the given name.
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 = "\\b(?<Geeks>[A-Za-z\\s]+)"; // Create a pattern from regex Pattern pattern = Pattern.compile(regex); // Get the String to be matched String stringToBeMatched = "GeeksForGeeks"; // 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("Geeks")); } }} |
Output:
Current Matcher: java.util.regex.Matcher[pattern=\b(?[A-Za-z\s]+) region=0,13 lastmatch=]
0
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 = "\\b(?<GFG>[A-Za-z\\s]+)"; // Create a pattern from regex Pattern pattern = Pattern.compile(regex); // Get the String to be matched String stringToBeMatched = " GFGFGFGFGFGFGFGFGFG"; // 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("GFG")); } }} |
Output:
Current Matcher: java.util.regex.Matcher[pattern=\b(?[A-Za-z\s]+) region=0,22 lastmatch=]
3
Reference: Oracle Doc
