Matcher regionStart() method in Java with Examples

// Java code to illustrate regionStart() method

import java.util.regex.*;

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

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

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

        // Get the String to be matched
        String stringToBeMatched
            = "GeeksForGeeks Geeks for For Geeks Geek";

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

        // Get previous startIndex of region
        // using regionStart() method
        System.out.println("Before changing region, "
                           + " Region starts from: "
                           + matcher.regionStart());

        // Restrict the region to 2, 10
        matcher = matcher.region(2, 10);

        // Get previous startIndex of region
        // using regionStart() method
        System.out.println("After changing region, "
                           + " Region starts from: "
                           + matcher.regionStart());
    }
}

// Java code to illustrate regionStart() method

import java.util.regex.*;

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

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

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

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

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

        // Get previous startIndex of region
        // using regionStart() method
        System.out.println("Before changing region, "
                           + " Region starts from: "
                           + matcher.regionStart());

        // Restrict the region to 5, 10
        matcher = matcher.region(5, 10);

        // Get previous startIndex of region
        // using regionStart() method
        System.out.println("After changing region, "
                           + " Region starts from: "
                           + matcher.regionStart());
    }
}