Optimization of JSON to XML conversion code

In one of my code we used below code snippit to convert JSON to XMl,

   DocumentBuilderFactory documentBuilderFactory =      DocumentBuilderFactory.newInstance();
    DocumentBuilder documentBuilder =     documentBuilderFactory.newDocumentBuilder();
    Document document = documentBuilder.newDocument();
    document = standardJsonToXML(hierarchyData, document, null);
     TransformerFactory transformerFactory =     TransformerFactory.newInstance();
    Transformer transformer = transformerFactory.newTransformer();
    DOMSource source = new DOMSource(document);
    StringWriter writer = new StringWriter();
   StreamResult result = new StreamResult(writer);

      transformer.transform(source, result);

   return writer.toString();

Please let me know How can I increase the performance of above code snippit