bom no java esse codigo estava funcionando normalmente, mudei pro java fx e estou com alguns problemas (já adicionei a biblioteca mysql)
codigo do con:
package Conexao;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.logging.Level;
import java.util.logging.Logger;
public class ConnectionFactory {
    private static final String DRIVER = "com.mysql.jdbc.Driver";
    private static final String URL = "jdbc:mysql://localhost:3306/helpsemeq"+"?verifyServerCertificate=false&useSSL=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=America/Sao_Paulo";
    private static final String USER = "root";
    private static final String PASS = "";
    private static Connection conexao;
    public Statement statement;
    public ResultSet resultset;
    public boolean getConnection() {
        boolean result = true;
        try {
            Class.forName(DRIVER);
            conexao = DriverManager.getConnection(URL, USER, PASS);
            result = true;
        } catch (ClassNotFoundException | SQLException ex) {
            result = false;
            throw new RuntimeException("Erro na conexão: ", ex);
        }
        return result;
    }
    public static void closeConnection(Connection con) {
        try {
            if (con != null) {
                con.close();
            }
        } catch (SQLException ex) {
            Logger.getLogger(ConnectionFactory.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    public static void closeConnection(Connection con, PreparedStatement stmt) {
        closeConnection(con);
        try {
            if (stmt != null) {
                stmt.close();
            }
        } catch (SQLException ex) {
            Logger.getLogger(ConnectionFactory.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    public static void closeConnection(Connection con, PreparedStatement stmt, ResultSet rs) {
        closeConnection(con, stmt);
        try {
            if (rs != null) {
                rs.close();
            }
        } catch (SQLException ex) {
            Logger.getLogger(ConnectionFactory.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    public void executeSQL(String sql) {
        try {
            statement = conexao.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
            resultset = statement.executeQuery(sql);
        } catch (SQLException sqlex) {
            System.out.println("Não foi possivel executar o comando: \n" + sqlex + "\n o sql passado foi: \n" + sql);
        }
    }
}
metodo e button:
@FXML
private Label label;
@FXML
private TextField jLogin;
@FXML
private PasswordField jSenha;
    @FXML
    private void handleButtonAction(ActionEvent event) {
        System.out.println("You clicked me!");
        label.setText("Hello World!");
    }
    @FXML
    private void validar(ActionEvent event) {
        validaLogin();
    }
    public void validaLogin(){
        try {
            ConnectionFactory conn = new ConnectionFactory();
            conn.getConnection();
            
            String sql = "SELECT login,senha FROM usuario where login = '" + jLogin.getText() + "' and  senha = '" + jSenha.getText() + "'";
            conn.executeSQL(sql);
            //Se houver resultado, ou seja, se validar o usuario e senha, faça algo.
            if (conn.resultset.next()) {
            System.out.println("Acesso negaado.");
            } else {
            System.out.println("Acesso negado.");
            }
        }catch(SQLException e){
            System.out.println("Erro: "+e);
        }
    }
codigo do error:
Exception in thread "JavaFX Application Thread" java.lang.RuntimeException: java.lang.reflect.InvocationTargetException
	at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1774)
	at javafx.fxml.FXMLLoader$ControllerMethodEventHandler.handle(FXMLLoader.java:1657)
	at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:86)
	at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
	at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
	at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
	at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:49)
	at javafx.event.Event.fireEvent(Event.java:198)
	at javafx.scene.Node.fireEvent(Node.java:8411)
	at javafx.scene.control.Button.fire(Button.java:185)
	at com.sun.javafx.scene.control.behavior.ButtonBehavior.mouseReleased(ButtonBehavior.java:182)
	at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:96)
	at com.sun.javafx.scene.control.skin.BehaviorSkinBase$1.handle(BehaviorSkinBase.java:89)
	at com.sun.javafx.event.CompositeEventHandler$NormalEventHandlerRecord.handleBubblingEvent(CompositeEventHandler.java:218)
	at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:80)
	at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:238)
	at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:191)
	at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:59)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:58)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:56)
	at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:114)
	at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:74)
	at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:54)
	at javafx.event.Event.fireEvent(Event.java:198)
	at javafx.scene.Scene$MouseHandler.process(Scene.java:3757)
	at javafx.scene.Scene$MouseHandler.access$1500(Scene.java:3485)
	at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1762)
	at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2494)
	at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:394)
	at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:295)
	at java.security.AccessController.doPrivileged(Native Method)
	at com.sun.javafx.tk.quantum.GlassViewEventHandler.lambda$handleMouseEvent$353(GlassViewEventHandler.java:432)
	at com.sun.javafx.tk.quantum.QuantumToolkit.runWithoutRenderLock(QuantumToolkit.java:389)
	at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:431)
	at com.sun.glass.ui.View.handleMouseEvent(View.java:555)
	at com.sun.glass.ui.View.notifyMouse(View.java:937)
	at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
	at com.sun.glass.ui.win.WinApplication.lambda$null$147(WinApplication.java:177)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.reflect.misc.Trampoline.invoke(MethodUtil.java:71)
	at sun.reflect.GeneratedMethodAccessor1.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at sun.reflect.misc.MethodUtil.invoke(MethodUtil.java:275)
	at javafx.fxml.FXMLLoader$MethodHandler.invoke(FXMLLoader.java:1769)
	... 48 more
Caused by: java.lang.NullPointerException
	at semeqapp.LoginFXController.validaLogin(LoginFXController.java:46)
	at semeqapp.LoginFXController.validar(LoginFXController.java:39)
	... 58 more
bom eu não tenho certeza, mas acho que o error está nessa parte:
String sql = "SELECT login,senha FROM usuario where login = '" + jLogin.getText() + "' and  senha = '" + jSenha.getText() + "'";
       conn.executeSQL(sql); ( qnd vou debugar ele pular essa parte)
        
) no título, também fica bem fácil ver o que já foi respondido e ainda tira a obrigação do usuário/moderador colocar tags no título. Fica até mais intuitivo! 