Output line number for SAX parser event handler in Java

import java.io.StringReader;
/*from   w  ww.  ja  v a2  s . c  o  m*/
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.Attributes;
import org.xml.sax.InputSource;
import org.xml.sax.Locator;
import org.xml.sax.SAXException;
import org.xml.sax.helpers.DefaultHandler;

public class Main {
  public static void main(String[] argv) throws Exception {
    SAXParserFactory factory = SAXParserFactory.newInstance();
    factory.setValidating(true);
    SAXParser parser = factory.newSAXParser();
    SampleOfXmlLocator handler = new SampleOfXmlLocator();
    //parser.parse("xmlFileName.xml", handler);
    
    StringReader sr = new StringReader("<folks></folks>");
    InputSource is = new InputSource(sr);
    parser.parse(is, handler);
    
  }
}

class SampleOfXmlLocator extends DefaultHandler {
  private Locator locator;
  public void setDocumentLocator(Locator locator) {
    this.locator = locator;
  }
  public void startElement(String uri, String localName, String qName, Attributes attrs)
      throws SAXException {
    if (qName.equals("order")) {
      System.out.println("here process element start");
    } else {
      String location = "";
      if (locator != null) {
        location = locator.getSystemId(); // XML-document name;
        location += " line " + locator.getLineNumber();
        location += ", column " + locator.getColumnNumber();
        location += ": ";
      }
      throw new SAXException(location + "Illegal element");
    }
  }
  public static void main(String[] args) throws Exception {
    SAXParserFactory factory = SAXParserFactory.newInstance();
    factory.setValidating(true);
    SAXParser parser = factory.newSAXParser();
    parser.parse("sample.xml", new SampleOfXmlLocator());
  }
}