JavaFX Pusta tabelka

Kod Main.java

package sample;

import javafx.application.Application;
import javafx.stage.Stage;
import javafx.scene.Scene;
import javafx.scene.layout.VBox;
import javafx.scene.control.TableView;
import javafx.scene.control.TableColumn;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.collections.ObservableList;
import javafx.collections.FXCollections;


public class Main extends Application{
    private Stage window;
    TableView<Wokers> table;

    public static void main(String[] args){
        launch(args);
    }
    public void start(Stage primaryStage) throws Exception{
        window = primaryStage;
        window.setTitle("tableViewExample");

        TableColumn<Wokers, Integer> idColumn = new TableColumn<>("Id");
        idColumn.setMinWidth(100);
        idColumn.setCellValueFactory(new PropertyValueFactory<Wokers, Integer>("Id"));

        TableColumn<Wokers, String> nameColumn = new TableColumn<>("Name");
        nameColumn.setMinWidth(100);
        nameColumn.setCellValueFactory(new PropertyValueFactory<Wokers, String>("Name"));

        TableColumn<Wokers, String> surnameColumn = new TableColumn<>("Surname");
        surnameColumn.setMinWidth(150);
        surnameColumn.setCellValueFactory(new PropertyValueFactory<Wokers, String>("Surname"));

        TableColumn<Wokers, String> positionColumn = new TableColumn<>("Position");
        positionColumn.setMinWidth(100);
        positionColumn.setCellValueFactory(new PropertyValueFactory<Wokers, String>("Position"));

        TableColumn<Wokers, Double> salaryColumn = new TableColumn<>("Salary");
        salaryColumn.setMinWidth(100);
        salaryColumn.setCellValueFactory(new PropertyValueFactory<Wokers, Double>("Salary"));

        ObservableList<Wokers> woker = FXCollections.observableArrayList();
        woker.add(new Wokers(1, "a", "Laptop", "a", 1199));
        woker.add(new Wokers(2, "bb", "cc", "aaa", 1999));

        table = new TableView<>();
        table.setItems(woker);
        table.getColumns().addAll(idColumn, nameColumn, surnameColumn, positionColumn, salaryColumn);

        VBox vBox = new VBox();
        vBox.getChildren().add(table);

        Scene scene = new Scene(vBox, 532, 200);

        window.setScene(scene);
        window.show();
    }
}

Kod Wokers.java

package sample;

/**
 * Created by root on 04.05.17.
 */
public class Wokers {

    private int id;
    private String name;
    private String surname;
    private String position;
    private double salary;

    public Wokers(){
        this.id = 0;
        this.name = "";
        this.surname = "";
        this.position = "";
        this.salary = 0;
    }

    public Wokers(int id, String name, String surname, String position, double salary){
        this.id = id;
        this.name = name;
        this.surname = surname;
        this.position = position;
        this.salary = salary;
    }

    //setters

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

    void setName(String name){
        this.name = name;
    }

    void setSurname(String surname){
        this.surname = surname;
    }

    void setPosition(String position){
        this.position = position;
    }

    void setSalary(double salary){
        this.salary = salary;
    }

    //getters

    int getId(){
        return this.id;
    }

    String getName(){
        return this.name;
    }

    String getSurname(){
        return this.surname;
    }

    String getPosition(){
        return this.position;
    }

    double getSalary(){
        return this.salary;
    }
}

Pytanie. Dlaczego wyświetla się pusta tabelka mimo dodania do niej elementów?