<data>
 <employee>
    <name>John</name>
    <title>Manager</title>
 </employee>
 <employee>
    <name>Sara</name>
    <title>Clerk</title>
    </employee>
</data>

import java.io.File;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathFactory;

import org.w3c.dom.Document;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;

public class XMLReplaceDemo {
  static String inputFile = "C:/temp/data.xml";
  static String outputFile = "C:/temp/data_new.xml";

  public static void main(String[] args) throws Exception {
    Document doc = DocumentBuilderFactory.newInstance()
        .newDocumentBuilder().parse(new InputSource(inputFile));

    // locate the node(s)
    XPath xpath = XPathFactory.newInstance().newXPath();
    NodeList nodes = (NodeList)xpath.evaluate
        ("//employee/name[text()='John']", doc, XPathConstants.NODESET);

    // make the change
    for (int idx = 0; idx < nodes.getLength(); idx++) {
      nodes.item(idx).setTextContent("John Paul");
    }
 
    // save the result
    Transformer xformer = TransformerFactory.newInstance().newTransformer();
    xformer.transform
        (new DOMSource(doc), new StreamResult(new File(outputFile)));
  }
}

<?xml version="1.0" encoding="UTF-8" standalone="no"?><data>
 <employee>
    <name>John Paul</name>
    <title>Manager</title>
 </employee>
 <employee>
    <name>Sara</name>
    <title>Clerk</title>
    </employee>
</data>