java.util.regex.Matcher.start() Method

Description

The java.util.regex.Matcher.start() method returns the start index of the previous match.

Declaration

Following is the declaration for java.util.regex.Matcher.start() method.

public int start()

Return Value

The index of the first character matched.

Exceptions

• IllegalStateException − If no match has yet been attempted, or if the previous match operation failed.

Example

The following example shows the usage of java.util.regex.Matcher.start() method.

package com.tutorialspoint;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class MatcherDemo {
   private static String REGEX = "(a*b)(foo)";
   private static String INPUT = "aabfooaabfooabfoob";
   private static String REPLACE = "-";
   
   public static void main(String[] args) {
      Pattern pattern = Pattern.compile(REGEX);
      
      // get a matcher object
      Matcher matcher = pattern.matcher(INPUT);
      
      while(matcher.find()) {
         //Prints the start index of the previous match.
         System.out.println("First Capturing Group, (a*b) Match String start(): "+matcher.start());    
      }      
   }
}

Let us compile and run the above program, this will produce the following result −

First Capturing Group, (a*b) Match String start(): 0
First Capturing Group, (a*b) Match String start(): 6
First Capturing Group, (a*b) Match String start(): 12