public static void evaluerDOM(Document document, String expression, QName retour){
   try{
      //création du XPath 
      XPathFactory fabrique = XPathFactory.newInstance();
      XPath xpath = fabrique.newXPath();

      //évaluation de l'expression XPath
      XPathExpression exp = xpath.compile(expression);
      Object resultat = exp.evaluate(document,retour);

      System.out.println(resultat);
   }catch(XPathExpressionException xpee){
      xpee.printStackTrace();
   }
}

public static void evaluerSAX(File fichier, String expression, QName retour){
   try{
      //création de la source
      InputSource source = new InputSource(new FileInputStream(fichier));

      //création du XPath 
      XPathFactory fabrique = XPathFactory.newInstance();
      XPath xpath = fabrique.newXPath();

      //évaluation de l'expression XPath
      XPathExpression exp = xpath.compile(expression);
      Object resultat = exp.evaluate(source,retour);

      System.out.println(resultat);
   }catch(XPathExpressionException xpee){
      xpee.printStackTrace();
   }catch(IOException  ioe){
      ioe.printStackTrace();
   }
}

   XPath xpath = XPathFactory.newInstance().newXPath();
   Object resultat = xpath.evaluate(expression,document,retour);

NamespaceContext namespace = new NamespaceContext(){
   public String getNamespaceURI(String prefix){
      if("content".equals(prefix)){
         return "http://purl.org/rss/1.0/modules/content/";
      }else{
         return null;
      }
   }
   public String getPrefix(String namespaceURI){
      if("http://purl.org/rss/1.0/modules/content/".equals(namespaceURI)){
         return "content";
      }else{
         return null;
      }
   }
   public Iterator getPrefixes(String namespaceURI){
      return null;
   } 
};
XPathFactory fabrique = XPathFactory.newInstance();
XPath xpath = fabrique.newXPath();
xpath.setNamespaceContext(namespace);

public static NodeList evaluer(InputStream stream, String expression){
   NodeList liste = null;
   try{
      //création de la source
      InputSource source = new InputSource(stream);

      //création du XPath 
      XPathFactory fabrique = XPathFactory.newInstance();
      XPath xpath = fabrique.newXPath();

      //évaluation de l'expression XPath
      XPathExpression exp = xpath.compile(expression);
      liste = (NodeList)exp.evaluate(source,XPathConstants.NODESET);

   }catch(XPathExpressionException xpee){
      xpee.printStackTrace();
   }
   return liste;
}

URL url = new URL("http://blog.developpez.com/xmlsrv/rss2.php?blog=1");

String expression = "//item/title";

System.out.println("Articles disponibles sur le blog de developpez.com");
NodeList liste = evaluer(url.openStream(),expression);
if(liste != null){
   for(int i=0; i<liste.getLength(); i++){
      Node node = liste.item(i);
      System.out.println(node.getTextContent());
   }
}

public static Node evaluer(InputStream stream, String expression){
   Node node = null;
   try{
      //création de la source
      InputSource source = new InputSource(stream);

      //création du XPath 
      XPathFactory fabrique = XPathFactory.newInstance();
      XPath xpath = fabrique.newXPath();

      //évaluation de l'expression XPath
      XPathExpression exp = xpath.compile(expression);
      node = (Node)exp.evaluate(source,XPathConstants.NODE);

   }catch(XPathExpressionException xpee){
      xpee.printStackTrace();
   }
   return node;
}

URL url = new URL("http://blog.developpez.com/xmlsrv/rss2.php?blog=12");

String expression = "rss/channel/item/title";

Node node = evaluer(url.openStream(),expression);
System.out.println(node.getTextContent());

public static Boolean evaluer(InputStream stream, String expression){
   Boolean b = null;
   try{
      //création de la source
      InputSource source = new InputSource(stream);

      //création du XPath 
      XPathFactory fabrique = XPathFactory.newInstance();
      XPath xpath = fabrique.newXPath();

      //évaluation de l'expression XPath
      XPathExpression exp = xpath.compile(expression);
      b = (Boolean)exp.evaluate(source,XPathConstants.BOOLEAN);

   }catch(XPathExpressionException xpee){
      xpee.printStackTrace();
   }
   return b;
}

URL url = new URL("http://blog.developpez.com/xmlsrv/rss2.php?blog=1");

String expression = "rss/channel/item[position()=1 and contains(./link/text(),'blog=12')]";

Boolean b = evaluer(url.openStream(),expression);
String s = "";
if(b){
   s = "Le premier message du blog de developpez.com appartient à la rubrique Java";
}else{
   s = "Le premier message du blog de developpez.com n'appartient pas à la rubrique Java";
}
System.out.println(s);

public static String evaluer(InputStream stream, String expression, 
                                             NamespaceContext namespace){
   String string = null;
   try{
      //création de la source
      InputSource source = new InputSource(stream);

      //création du XPath 
      XPathFactory fabrique = XPathFactory.newInstance();
      XPath xpath = fabrique.newXPath();
      if(namespace != null){
         xpath.setNamespaceContext(namespace);
      }

      //évaluation de l'expression XPath
      XPathExpression exp = xpath.compile(expression);
      string = (String)exp.evaluate(source,XPathConstants.STRING);

   }catch(XPathExpressionException xpee){
      xpee.printStackTrace();
   }
   return string;
}

URL url = new URL("http://blog.developpez.com/xmlsrv/rss2.php?blog=1");

String expression = "//item/content:encoded";
NamespaceContext namespace = new NamespaceContext(){
   public String getNamespaceURI(String prefix){
      if("content".equals(prefix)){
         return "http://purl.org/rss/1.0/modules/content/";
      }else{
         return null;
      }
   }
   public String getPrefix(String namespaceURI){
      if("http://purl.org/rss/1.0/modules/content/".equals(namespaceURI)){
         return "content";
      }else{
         return null;
      }
   }
   public Iterator getPrefixes(String namespaceURI){
      return null;
   } 
};

String article = evaluer(url.openStream(),expression,namespace);

JTextPane pane = new JTextPane();
pane.setContentType("text/html");
pane.setPreferredSize(new Dimension(200,200));
JScrollPane scroll = new JScrollPane(pane);

JFrame frame = new JFrame();
//etc.
frame.setVisible(true);

pane.setText(article);

public static Double evaluer(InputStream stream, String expression){
   Double number = null;
   try{
      //création de la source
      InputSource source = new InputSource(stream);

      //création du XPath 
      XPathFactory fabrique = XPathFactory.newInstance();
      XPath xpath = fabrique.newXPath();

      //évaluation de l'expression XPath
      XPathExpression exp = xpath.compile(expression);
      number = (Double)exp.evaluate(source,XPathConstants.NUMBER);

   }catch(XPathExpressionException xpee){
      xpee.printStackTrace();
   }
   return number;
}

URL url = new URL("http://blog.developpez.com/xmlsrv/rss2.php?blog=12");

String expression = "count(rss/channel/item/category[text()='3. Technologie J2EE'])";

Double number = evaluer(url.openStream(),expression);
System.out.println("Il y a "+number+" news J2EE sur le blog de la rubrique Java");