Recuperar un boolean a partir de una expresión XPath

public static Boolean evaluador(InputStream stream, String expression){
   Boolean b = null;
   try{
      // creación del source
      InputSource source = new InputSource(stream);
 
      // creación del XPath 
      XPathFactory factory = XPathFactory.newInstance();
      XPath xpath = factory.newXPath();
 
      // evaluar la expresión XPath
      XPathExpression exp = xpath.compile(expression);
      b = (Boolean)exp.evaluate(source,XPathConstants.BOOLEAN);
   }catch(XPathExpressionException xpee){
      xpee.printStackTrace();
   }
   return b;
}