The code below displays a TableView with 20 columns. The columns don't fit on the screen so I would expect a horizontal scroll bar to be displayed. It is not. If I add some items to the TableView then the scroll bar is displayed as expected.

import javafx.application.Application;
import javafx.beans.property.ReadOnlyStringWrapper;
import javafx.collections.FXCollections;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

import java.util.ArrayList;
import java.util.List;

public class ManyColumnsTest extends Application {
    @Override
    public void start(Stage stage) throws Exception {
        BorderPane pane = new BorderPane();
        Scene scene = new Scene(pane, 500, 500);
        stage.setScene(scene);

        int numColumns = 20;
        TableView<String[]> table = new TableView<>();
        for (int i = 0; i < numColumns; i++) {
            final int column = i;
            TableColumn<String[], String> childColumn = new TableColumn<>("Child Column " + i);
            childColumn.setCellValueFactory(stringCellDataFeatures -> new ReadOnlyStringWrapper(stringCellDataFeatures.getValue()[column]));
            table.getColumns().add(childColumn);
        }
        List<String[]> data = new ArrayList<>(5);
        for (int j = 0; j < 5; j++) {
            String[] row = new String[numColumns];
            for (int i = 0; i < numColumns; i++) {
                row[i] = "(" + j + ", " + i + ")";
            }
            data.add(row);
        }
// table.setItems(FXCollections.observableArrayList(data));

        pane.setCenter(table);
        stage.show();
    }

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