在JavaFX文本字段中输入文本之前显示不可删除的文本

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        TextField textField = new TextField();
        textField.setPromptText("请输入文本");

        VBox root = new VBox(textField);
        Scene scene = new Scene(root, 200, 100);

        primaryStage.setTitle("JavaFX Text Field");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

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