jdom xpath查找节点

List namesList=null;                try {                    namesList = XPath.selectNodes(doc.getRootElement(), "//username");                } catch (JDOMException ex) {                    Logger.getLogger(FormListLogic.class.getName()).log(Level.SEVERE, null, ex);                }

 List namesList=null;                try {                    namesList = XPath.selectNodes(doc.getRootElement(), "/root/cell/username");                } catch (JDOMException ex) {                    Logger.getLogger(FormListLogic.class.getName()).log(Level.SEVERE, null, ex);                }