import java.io.*;
import org.w3c.dom.*;
import javax.xml.parsers.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;

public class UpdateXML {
    public static void main(String args[]) {
        try {
            File file = new File("c:/new.xml");
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder docBuilder = factory.newDocumentBuilder();
            Document doc = docBuilder.parse(file);
            Element root = doc.getDocumentElement();
            Element element = (Element) doc.getElementsByTagName("Address").item(0);
            Element childElement = doc.createElement("ContactNo");
            root.replaceChild(childElement, element);
            TransformerFactory transfac = TransformerFactory.newInstance();
            Transformer trans = transfac.newTransformer();

            StringWriter sw = new StringWriter();
            StreamResult result = new StreamResult(sw);
            DOMSource source = new DOMSource(doc);
            trans.transform(source, result);
            String xmlString = sw.toString();
            OutputStream os;
            byte buf[] = xmlString.getBytes();
            os = new FileOutputStream("C:/new.xml");
            for (int i = 0; i < buf.length; i++) {
                os.write(buf[i]);
            }
            os.close();
            buf = null;
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}