Can not retrieve property in PropertyValueFactory

Witam mam problem z wyświetleniem tabeli w JavieFX

polowe wyświetla, a na połowie kolumn wyrzuca błędy:

WARNING:  Can not retrieve property 'numer_grupy' in PropertyValueFactory: javafx.scene.control.cell.PropertyValueFactory@1e9f6477 with provided class type: class pl.dziennik.ModelStudentList
 java.lang.IllegalStateException: Cannot read from unreadable property numer_grupy

 WARNING: Can not retrieve property 'rok_studiow' in PropertyValueFactory: javafx.scene.control.cell.PropertyValueFactory@4d06501f with provided class type: class pl.dziennik.ModelStudentList
 java.lang.IllegalStateException: Cannot read from unreadable property rok_studiow

Controller:

package pl.dziennik;

import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;

import java.net.URL;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ResourceBundle;

public class ControllerStudentList implements Initializable {
    Connection c = null;
    Statement stmt = null;

    @FXML
    private TableView<ModelStudentList> tabelaListyStudentow;
    @FXML
    private TableColumn<ModelStudentList, Integer> kolumnaId;
    @FXML
    private TableColumn<ModelStudentList, String> kolumnaImie;
    @FXML
    private TableColumn<ModelStudentList, String> kolumnaNazwisko;

    @FXML
    private TableColumn<ModelStudentList, Integer> kolumnaNrGrupy;

    @FXML
    private TableColumn<ModelStudentList, Integer> kolumnaRokStudiow;


    ObservableList<ModelStudentList> listaDoTabeli = FXCollections.observableArrayList();

    @Override
    public void initialize(URL location, ResourceBundle resources) {
        try {
            Class.forName("org.sqlite.JDBC");
            c = DriverManager.getConnection("jdbc:sqlite:C:\\xampp\\htdocs\\java-projek\\bazaDziekanat");
            System.out.println("Polaczenie z baza: poprawne");
        } catch (Exception e) {
            System.out.println("Polaczenie z baza: niepoprawne: " + e.getMessage());
        }
        try {
            this.stmt = c.createStatement();

            ResultSet rs = stmt.executeQuery("SELECT * FROM Student");

            while(rs.next()) {
                listaDoTabeli.add(new ModelStudentList(rs.getInt("id"),
                        rs.getString("imie"), rs.getString("nazwisko"),
                        rs.getInt("numer_grupy"), rs.getInt("rok_studiow")));

            }
        } catch (Exception e) {
            System.out.println("Blad: " + e.getMessage());
        }

        kolumnaId.setCellValueFactory(new PropertyValueFactory<>("id"));
        kolumnaImie.setCellValueFactory(new PropertyValueFactory<>("imie"));
        kolumnaNazwisko.setCellValueFactory(new PropertyValueFactory<>("nazwisko"));
        kolumnaNrGrupy.setCellValueFactory(new PropertyValueFactory<>("numer_grupy"));
        kolumnaRokStudiow.setCellValueFactory(new PropertyValueFactory<>("rok_studiow"));
        tabelaListyStudentow.setItems(listaDoTabeli);
    }

}

Model

package pl.dziennik;

public class ModelStudentList {

    private int id, numer_grupy, rok_studiow;
    private String imie, nazwisko;


    public ModelStudentList(int id, String imie, String nazwisko, int numer_grupy, int rok_studiow) {
        this.id = id;
        this.imie= imie;
        this.nazwisko = nazwisko;
        this.numer_grupy = numer_grupy;
        this.rok_studiow = rok_studiow;
    }



    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }


    public String getImie() {
        return imie;
    }

    public void setImie(String imie) {
        this.imie = imie;
    }



    public String getNazwisko() {
        return nazwisko;
    }

    public void setNazwisko(String nazwisko) {
        this.nazwisko = nazwisko;
    }


    public int getNumerGrupy() {
        return numer_grupy;
    }

    public void setNumerGrup(int numer_grupy) {
        this.numer_grupy = numer_grupy;
    }


    public int getRokStudiow() {
        return rok_studiow;
    }

    public void setRokStudiow(int rok_studiow) {
        this.rok_studiow = rok_studiow;
    }

}

FXML:

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.control.TableColumn?>
<?import javafx.scene.control.TableView?>
<?import javafx.scene.layout.AnchorPane?>


<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="400.0" minWidth="641.0" prefHeight="400.0" prefWidth="641.0" xmlns="http://javafx.com/javafx/11.0.1" xmlns:fx="http://javafx.com/fxml/1" fx:controller="pl.dziennik.ControllerStudentList">
   <children>
      <TableView fx:id="tabelaListyStudentow" layoutX="147.0" layoutY="68.0" prefHeight="400.0" prefWidth="700.0" AnchorPane.bottomAnchor="0.0" AnchorPane.leftAnchor="0.0" AnchorPane.rightAnchor="0.0" AnchorPane.topAnchor="0.0">
        <columns>
          <TableColumn fx:id="kolumnaId" prefWidth="29.00000035762787" text="ID" />
          <TableColumn fx:id="kolumnaImie" prefWidth="162.99999046325684" text="Imie" />
            <TableColumn fx:id="kolumnaNazwisko" prefWidth="160.0" text="Nazwisko" />
            <TableColumn fx:id="kolumnaNrGrupy" prefWidth="117.79998779296875" text="Nr grupy" />
            <TableColumn fx:id="kolumnaRokStudiow" prefWidth="119.79995727539062" text="Rok studiow" />
        </columns>
      </TableView>
   </children>
</AnchorPane>

Robiąc klasę modelową z danymi i bindując ją z kontrolkami w JavaFX, nie używa się typów jak String/int tylko IntegerProperty/StringProperty