HttpSession httpSession=request.getSession(false);

This line of code retrieves the existing HttpSession object associated with the current request, or returns null if there is no current session and the "false" parameter is passed. The "false" parameter indicates that the method should not create a new session if one does not already exist. By default, if no parameter is passed or if "true" is passed, a new session will be created if one does not already exist.