Displaying JavaFX TableView row number in a column

IndexColumnDemo.java

import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.binding.ObjectBinding;
import javafx.beans.property.ReadOnlyObjectProperty;
import javafx.beans.property.ReadOnlyObjectWrapper;
import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.TableCell;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableRow;
import javafx.scene.control.TableView;
import javafx.stage.Stage;

public class IndexColumnDemo extends Application {
  @Override
  public void start(Stage stage) {
    stage.setTitle("Table height example");

    TableView<String> table = new TableView<>(FXCollections.observableArrayList(
      "Stacey", "Kristy", "Mary Anne", "Claudia"
    ));

    TableColumn<String, Integer> indexColumn = new TableColumn<>();
    indexColumn.setCellFactory(col -> {
      TableCell<String, Integer> indexCell = new TableCell<>();
      ReadOnlyObjectProperty<TableRow<String>> rowProperty = indexCell.tableRowProperty();
      ObjectBinding<String> rowBinding = Bindings.createObjectBinding(() -> {
        TableRow<String> row = rowProperty.get();
        if (row != null) {
          int rowIndex = row.getIndex();
          if (rowIndex < row.getTableView().getItems().size()) {
            return Integer.toString(rowIndex);
          }
        }
        return null;
      }, rowProperty);
      indexCell.textProperty().bind(rowBinding);
      return indexCell;
    });

    TableColumn<String, String> nameColumn = new TableColumn<>("name");
    nameColumn.setCellValueFactory(f -> new ReadOnlyObjectWrapper<>(f.getValue()));

    ObservableList<TableColumn<String, ?>> columns = table.getColumns();
    columns.add(indexColumn);
    columns.add(nameColumn);

    Group root = new Group();
    root.getChildren().add(table);
    Scene scene = new Scene(root);
    stage.setScene(scene);
    stage.show();

    stage.sizeToScene();
  }

  public static void main(String[] args) {
    launch(args);
  }
}

@BuiHoangTu I haven't looked at JavaFX in years (and haven't been doing much Java at all lately) but it looks like your SimpleStringProperty is calling toString() on the ObjectBinding itself. That's not going to get you the bound value, it's just going to get you the string representation of the binding object.

You'll notice that in my code it's not an ObjectBinding<Integer>, it's an ObjectBinding<String> (which could probably be a StringBinding, actually), and the int to String conversion happens inside the binding (see line 34).