code: private String getRootId()
      {
          if ( rootId == null ) {
              rootId = getLogin().getElementsByTagName( "home" ).item( 0 ).getTextContent();
          }
  
          return rootId;
      }
docs: Gets the id of root folder.
  <p/>
  If the root id is already known it is returned else it is fetched then cached.
  
  @return the id of the root folder