Java CheckBox .indeterminateProperty ()

public final BooleanProperty indeterminateProperty()

import javafx.application.Application;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.CheckBox;
import javafx.stage.Stage;
//from ww  w .ja v a 2s .c  o  m
public class Main extends Application {
    public static void main(String[] args) {
        launch(args);
    }
    @Override
    public void start(Stage stage) {
        Scene scene = new Scene(new Group());
        stage.setWidth(300);
        stage.setHeight(150);
        final CheckBox cb = new CheckBox();
        cb.setText("checkBox");
        cb.setAllowIndeterminate(true);
        
        cb.indeterminateProperty().addListener(new ChangeListener<Boolean>() {
           public void changed(ObservableValue<? extends Boolean> ov,
             Boolean old_val, Boolean new_val) {
             System.out.println(cb.isSelected());
          }
        });
        ((Group) scene.getRoot()).getChildren().add(cb);

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