xpathAPI

    /**
     * Load a document from a file
     */
    public static Document loadDocument(String filename) {
        try {
            // Create a builder factory
            DocumentBuilderFactory factory = 
                DocumentBuilderFactory.
                newInstance();

            // Create the builder
            DocumentBuilder builder =
                factory.
                newDocumentBuilder();

            // Deserialization by parsing
            Document doc =
                builder.
                parse(new File(filename));

            // Done
            return doc;

        } catch (SAXException e) {
        } catch (ParserConfigurationException e) {
        } catch (IOException e) {
        }
        
        // Return null for any sort of problem
        return null;
    }

    /**
     * Save a document to a file.
     */
    public static boolean saveDocument(Document doc, String filename) {

        try {

            // Prepare the DOM document for writing
            Source source = new DOMSource(doc);

            // Prepare the output file
            File file = new File(filename);
            Result result = new StreamResult(file);

            // Creater a transformer factory
            TransformerFactory xfactory = 
                TransformerFactory.
                newInstance();

            // Create a transformer
            Transformer transformer = 
                xfactory.
                newTransformer();

            // Force pretty printing
            transformer.setOutputProperty(OutputKeys.METHOD, "xml");
            transformer.setOutputProperty(OutputKeys.INDENT, "yes");
            transformer.setOutputProperty("{http://xml.apache.org/xslt}indent-amount", "2");
            transformer.setOutputProperty(OutputKeys.ENCODING, "UTF-8");

            // Serialization by transformation
            transformer.transform(source, result);

            // Done
            return true;

        } catch (TransformerConfigurationException e) {
        } catch (TransformerException e) {
        }

        // Return false for any sort of problem
        return false;
    }

    public static double total(Document doc) 
        throws Exception {

        // The aggregation variable 
        double total = 0;

        // Get the matching elements
        NodeList nodelist = XPathAPI.selectNodeList(doc, "//salary");

        // Process the elements in the nodelist
        for (int i=0; i<nodelist.getLength(); i++) {
            // Get element
            Element elem = (Element)nodelist.item(i);
            total += Double.parseDouble(elem.getTextContent());
        }
        return total;
    }