what the problem?

package login.pkgfinal;

import java.io.InputStream;



import java.util.logging.Level;



import java.util.logging.Logger;



import javafx.application.Application;



import javafx.fxml.FXMLLoader;



import javafx.fxml.Initializable;



import javafx.fxml.JavaFXBuilderFactory;



import javafx.scene.Scene;



import javafx.scene.layout.AnchorPane;



import javafx.stage.Stage;



import login.pkgfinal.login.model.User;



import login.pkgfinal.login.model.Admin;



import login.pkgfinal.login.security.Authenticator;



import java.sql.*;

public class Main extends Application {

private Stage stage;



private User loggedUser;



private final double MINIMUM_WINDOW_WIDTH = 390.0;



private final double MINIMUM_WINDOW_HEIGHT = 500.0;

public static void main(String[] args) {



Application.launch(Main.class, (java.lang.String[])null);



}

@Override



public void start(Stage primaryStage) throws ClassNotFoundException, SQLException {

Connection conn = null;



Statement stmt = null;



try{



//STEP 2: Register JDBC driver



Class.forName("com.mysql.jdbc.Driver");

//STEP 3: Open a connection



System.out.println("Connecting to database...");



Class.forName("com.mysql.jdbc.Driver");



conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/e_voting?zeroDateTimeBehavior=convertToNull","root ","");

//STEP 4: Execute a query



System.out.println("<?php ?>");



stmt = conn.createStatement();



String sql;



sql = "SELECT id, first, last, age FROM Employees";



ResultSet rs = stmt.executeQuery(sql);

stage = primaryStage;



stage.setTitle("Login Main");



stage.setMinWidth(MINIMUM_WINDOW_WIDTH);



stage.setMinHeight(MINIMUM_WINDOW_HEIGHT);



gotoLogin();



primaryStage.show();



} catch (Exception ex) {



Logger.getLogger(Main.class.getName()).log(Level.S EVERE, null, ex);



}



}

public User getLoggedUser() {



return loggedUser;



}



public boolean userLogging(String userId, String password){



if (Authenticator.validate(userId, password)) {



loggedUser = User.of(userId);



gotoPageVote();



return true;



} else {



return false;



}



}

void userLogout(){



loggedUser = null;



gotoLogin();



}

private void gotoPageVote() {



try {



PageVoteController pagevote = (PageVoteController) replaceSceneContent("PageVote.fxml");



pagevote.setApp(null);



} catch (Exception ex) {



Logger.getLogger(Main.class.getName()).log(Level.S EVERE, null, ex);



}



}

private void gotoLogin() {



try {



LoginController login = (LoginController) replaceSceneContent("Login.fxml");



login.setApp(null);



} catch (Exception ex) {



Logger.getLogger(Main.class.getName()).log(Level.S EVERE, null, ex);



}



}

private Initializable replaceSceneContent(String fxml) throws Exception {



FXMLLoader loader = new FXMLLoader();



InputStream in = Main.class.getResourceAsStream(fxml);



loader.setBuilderFactory(new JavaFXBuilderFactory());



loader.setLocation(Main.class.getResource(fxml));



AnchorPane page;



try {



page = (AnchorPane) loader.load(in);



} finally {



in.close();



}



Scene scene = new Scene(page, 800, 600);



stage.setScene(scene);



stage.sizeToScene();



return (Initializable) loader.getController();



}

}