XPath query that uses namespaces

  XPathFactory factory = XPathFactory.newInstance();
  XPath xpath = factory.newXPath();
  xpath.setNamespaceContext(new PersonalNamespaceContext());
  XPathExpression expr = xpath.compile(
    "//pre:book[pre:author='Neal Stephenson']/pre:title/text()"
  );

  Object result = expr.evaluate(doc, XPathConstants.NODESET);
  NodeList nodes = (NodeList) result;
  for (int i = 0; i < nodes.getLength(); i++) {
    System.out.println(nodes.item(i).getNodeValue()); 
  }