Check for valid session: isRequestedSessionIdValid() vs getSession(false)

I'm developing Java Servlets. At the point of checking whether a user is logged in, I want to check if the HTTP request has a valid session. For checking that, I have 2 possibilities:

(1)

protected void processRequest(HttpServletRequest request,         HttpServletResponse response) throws ServletException, IOException {    HttpSession session = request.getSession(false);    if (session != null) {        // user is logged in        ...    }}

Since I pass false as an argument, there is no new session created if there is no valid session existing already, and the function returns null, for what I can check.

Or I do:

(2)

    if (request.isRequestedSessionIdValid()) {        // user is logged in        ...    }

Is there any difference, any advantage/disadvantage? Or do both functions do more or less the same?