JavaFX ObservableList bind to ListView

import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.geometry.HPos;
import javafx.geometry.Insets;
import javafx.geometry.VPos;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.control.ListView;
import javafx.scene.layout.GridPane;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.stage.Stage;

public class Main extends Application {
    public static void main(String[] args) {
        Application.launch(args);/* www .  j a  v a  2s. com*/
    }    
    @Override
    public void start(Stage primaryStage) {
        primaryStage.setTitle("Creating and Working with ObservableLists");
        Group root = new Group();
        Scene scene = new Scene(root, 400, 250, Color.WHITE);
        
        // create a grid pane
        GridPane gridpane = new GridPane();
        gridpane.setPadding(new Insets(5));
        gridpane.setHgap(10);
        gridpane.setVgap(10);
        
        // candidates label
        Label candidatesLbl = new Label("Candidates");
        GridPane.setHalignment(candidatesLbl, HPos.CENTER);
        gridpane.add(candidatesLbl, 0, 0);
          
        Label langsLbl = new Label("Heroes");
        gridpane.add(langsLbl, 2, 0);
        GridPane.setHalignment(langsLbl, HPos.CENTER);
        
        // candidates
        final ObservableList<String> candidates = FXCollections.observableArrayList(
                "CSS",
                "HTML",
                "Java",
                "Javascript", 
                "SQL", 
                "C++", 
                "C", 
                "Python", 
                "Ruby");
        final ListView<String> candidatesListView = new ListView<String>(candidates);
        candidatesListView.setPrefWidth(150);
        candidatesListView.setPrefHeight(150);

        gridpane.add(candidatesListView, 0, 1);
        
        // heros
        final ObservableList<String> heroes = FXCollections.observableArrayList();
        final ListView<String> heroListView = new ListView<String>(heroes);
        heroListView.setPrefWidth(150);
        heroListView.setPrefHeight(150);

        gridpane.add(heroListView, 2, 1);

        Button sendRightButton = new Button(">");
        sendRightButton.setOnAction(new EventHandler<ActionEvent>() {

            public void handle(ActionEvent event) {
                String potential = candidatesListView.getSelectionModel().getSelectedItem();
                if (potential != null) {
                    candidatesListView.getSelectionModel().clearSelection();
                    candidates.remove(potential);
                    heroes.add(potential);
                }
            }
        });
        
        Button sendLeftButton = new Button("<");
        sendLeftButton.setOnAction(new EventHandler<ActionEvent>() {

            public void handle(ActionEvent event) {
                String notHero = heroListView.getSelectionModel().getSelectedItem();
                if (notHero != null) {
                    heroListView.getSelectionModel().clearSelection();
                    heroes.remove(notHero);
                    candidates.add(notHero);
                }
            }
        });
        
        VBox vbox = new VBox(5);
        vbox.getChildren().addAll(sendRightButton,sendLeftButton);
        
        gridpane.add(vbox, 1, 1);
        GridPane.setConstraints(vbox, 1, 1, 1, 2,HPos.CENTER, VPos.CENTER);
       
        root.getChildren().add(gridpane);        
        primaryStage.setScene(scene);
        primaryStage.show();
    }
}