how I can get rid of null pointer exception

Question

'here is login form page'

<form action="login">
    Enter user:<input type="text" value="user">
    Enter pass:<input type="password" value="pass">
    <input type="submit" value="login">
        
</form>

'here is login servlet class code'

public class Login extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        PrintWriter out = response.getWriter();

        String uname = request.getParameter("user");
        String pass = request.getParameter("pass");
    if (user.equals("Navin") && pass.equals("navin")) {
            response.sendRedirect("welcome.jsp");
        } else {
            response.sendRedirect("login.jsp");
        }
        
    }

}