Document doc = DOMXMLParser.parse("path\to\xml.file");

ByteArrayOutputStream baos =  new  ByteArrayOutputStream();

Transformer documentWriter = TransformerFactory.newInstance().newTransformer();
documentWriter.setOutputProperty(OutputKeys.METHOD, "xml");
documentWriter.setOutputProperty(OutputKeys.INDENT, "yes");
documentWriter.setOutputProperty(OutputKeys.ENCODING, "UTF-8");
 synchronized  (documentWriter) {
        documentWriter.transform( new  DOMSource(doc),  new  StreamResult(baos));
}

 return  baos.toString("UTF-8");

 public   static   void  doValid(String xml)  throws  ParserConfigurationException, IOException, SAXException {
        DocumentBuilder documentBuilder = DocumentBuilderFactory.newInstance().newDocumentBuilder();
         synchronized  (documentBuilder) {
            documentBuilder.parse( new  ByteArrayInputStream(xml.getBytes()));
        }
    }