try {

            Class.forName("com.mysql.cj.jdbc.Driver");
      //  out.println("driver loaded");
            Connection  con = DriverManager.getConnection("jdbc:mysql://localhost:3306/Hotel?useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC","root" ,"123456789");
            out.println("Connect");
            Statement  st =  con.createStatement();
            Statement stmt = con.createStatement();
            out.println("connection successfull");

            String check = ("SELECT res1.id_prenotazione, res1.typeroom, res1.arrivaldate, res1.departuredaten" +
                    "FROM reservation res1, reservation res2n" +
                    "WHERE ( res1.typeroom = res2.typeroom ) n" +
                    "AND res1.id_prenotazione != res2.id_prenotazionen" +
                    "AND (res1.arrivaldate <= res2.departuredate)n" +
                    "AND (res2.arrivaldate <= res1.departuredate)");


           // ResultSet rs2  = stmt.executeQuery(check);
            out.println("<h1> Stringa chek eseguita </h1>");

            if(check) { // THIS DOESN't WORK OF COURSE
            int rs =  st.executeUpdate("insert into reservation (login,email,typeroom,numroom,arrivaldate,departuredate)values ('"+login+"','"+email+"','"+typeroom+"','"+numroom+"','"+arrivaldate+"','"+departuredate+"')");
            }
            String getResultSet = ("SELECT count(*) FROM reservation WHERE arrivaldate ='"+arrivaldate+"'");
            String rs1 = ("SELECT count(*) FROM reservation WHERE arrivaldate");


            if (getResultSet != rs1) {
                int i=st.executeUpdate("DELETE FROM reservation WHERE id_prenotazione ='"+id_prenotazione+"'");

            }