尝试从JFXtras运行icalenderagenda时出现异常“JavaFX Application”

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import org.jfxtras.icalendaragenda.CalendarPicker;
import org.jfxtras.icalendaragenda.CalendarProvider;
import org.jfxtras.icalendaragenda.DefaultCalendarProvider;

public class ICalendarAgendaExample extends Application {
    @Override
    public void start(Stage primaryStage) {
        // 创建日历提供者
        CalendarProvider calendarProvider = new DefaultCalendarProvider();

        // 创建日历选择器
        CalendarPicker calendarPicker = new CalendarPicker(calendarProvider);

        // 创建布局并将日历选择器添加到布局中
        StackPane root = new StackPane();
        root.getChildren().add(calendarPicker);

        // 创建场景并设置到舞台
        Scene scene = new Scene(root, 800, 600);
        primaryStage.setTitle("iCalendar Agenda Example");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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