当用户忘记选择一个单选按钮并立即使用java单击继续命令按钮时，如何提示警告消息？

import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

public class MainFrame extends JFrame {
    private JRadioButton radioButton;
    private JButton continueButton;

    public MainFrame() {
        // 初始化界面和组件

        radioButton = new JRadioButton("选项");
        continueButton = new JButton("继续");

        continueButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                if (!radioButton.isSelected()) {
                    JOptionPane.showMessageDialog(MainFrame.this, "请先选择一个选项");
                } else {
                    // 执行继续操作
                }
            }
        });

        // 添加组件到界面
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                MainFrame frame = new MainFrame();
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.pack();
                frame.setVisible(true);
            }
        });
    }
}