Checking null strings for check box using else if statement

I'm making a web app with 2 check boxes. I used this code to capture the check box value.

`@WebServlet(name = "cookie", urlPatterns = {"/cookie"})`

public class cookie extends HttpServlet {

@Override

public void service(HttpServletRequest request,HttpServletResponse response) throws IOException{
    String uname = request.getParameter("username");
    String password = request.getParameter("password");
    PrintWriter out = response.getWriter();
    String secf = request.getParameter("secf");
    String hof = request.getParameter("hof");
    if(uname.equals("admin") && password.equals("admin")){
        if(secf == null ? hof ==null : secf.equals(hof)){
            out.print("both nc");
        }
        else if(secf.equals("sfTrue")&& hof==null){
            out.print("sf t");
        }
        else if(hof.equals("hofTrue")&& secf==null){
            out.print("ho t");
        }
        else 
        {
            out.print("b c");
        }

            out.print("both not checked");*
        }
        else
            out.print("Cheked");*/
    }
    else
       out.print("Fail");
}

But the problem is when the hof is checked it throws nullpointer exception. Other incidents works