Servelet

Bonjour, j ai un problem dans la ligne soulignee , il me demande de changer le type de return

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {


{// TODO Auto-generated method stub
Etudiant am = new Etudiant();


String email=req.getParameter("email");
String password=req.getParameter("password");
String msg;
BeansEtudiant bs=new BeansEtudiant();
TrEtudiant tr=new TrEtudiant();

bs.setLs( tr.authent(email, password));
am=bs.getLs();
if(email.trim().isEmpty() || password.trim().isEmpty()){
msg="Veuillez remplir les champs";
req.setAttribute("msg", msg);
this.getServletContext().getRequestDispatcher("/login.jsp").forward(req, resp);
//req.getRequestDispatcher(arg0)
}else{
if((am.getEmail()==email) &&(am.getPassword()==password))
{

resp.sendRedirect("inc/index.jsp");
}else{

msg="Votre login ou mot de passe est incorrecte";
req.setAttribute("msg", msg);
this.getServletContext().getRequestDispatcher("/login.jsp").forward(req, resp);
}

}