如何在Java中为JComboBox添加分隔符？

import javax.swing.*;
import java.awt.*;

public class JComboBoxSeparator {
    public static void main(String[] args) {
        SwingUtilities.invokeLater(() -> createAndShowGUI());
    }

    private static void createAndShowGUI() {
        JFrame frame = new JFrame("JComboBox Separator Example");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(300, 200);

        DefaultComboBoxModel<String> model = new DefaultComboBoxModel<>();
        model.addElement("Option 1");
        model.addElement("Option 2");
        model.addElement("Option 3");
        model.addElement("Option 4");

        JComboBox<String> comboBox = new JComboBox<>(model);
        comboBox.setRenderer(new SeparatorRenderer());

        frame.getContentPane().add(comboBox, BorderLayout.NORTH);
        frame.setVisible(true);
    }

    private static class SeparatorRenderer extends DefaultListCellRenderer {
        @Override
        public Component getListCellRendererComponent(JList<?> list, Object value, int index, boolean isSelected, boolean cellHasFocus) {
            super.getListCellRendererComponent(list, value, index, isSelected, cellHasFocus);

            if (index == 2) {
                setEnabled(false);
                setText("---");
            }

            return this;
        }
    }
}