TableView为空

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.stage.Stage;

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

public class TableViewExample extends Application {

    @Override
    public void start(Stage primaryStage) {
        TableView<DataItem> tableView = new TableView<>();

        TableColumn<DataItem, String> column1 = new TableColumn<>("Column 1");
        column1.setCellValueFactory(new PropertyValueFactory<>("property1"));

        TableColumn<DataItem, Integer> column2 = new TableColumn<>("Column 2");
        column2.setCellValueFactory(new PropertyValueFactory<>("property2"));

        tableView.getColumns().addAll(column1, column2);

        List<DataItem> dataList = getData();
        tableView.setItems(dataList);

        Scene scene = new Scene(tableView, 300, 250);
        primaryStage.setTitle("TableView Example");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    private List<DataItem> getData() {
        List<DataItem> dataList = new ArrayList<>();
        // 添加数据到 dataList
        dataList.add(new DataItem("Value1", 1));
        dataList.add(new DataItem("Value2", 2));
        return dataList;
    }

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

class DataItem {
    private String property1;
    private int property2;

    public DataItem(String property1, int property2) {
        this.property1 = property1;
        this.property2 = property2;
    }

    public String getProperty1() {
        return property1;
    }

    public int getProperty2() {
        return property2;
    }
}