如何将JFileChooser限制为目录？

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

public class DirectoryChooser {
    public static void main(String[] args) {
        JFrame frame = new JFrame("Directory Chooser");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 300);

        JFileChooser fileChooser = new JFileChooser();
        fileChooser.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);

        JButton selectDirectoryButton = new JButton("Select Directory");
        selectDirectoryButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                int result = fileChooser.showOpenDialog(frame);
                if (result == JFileChooser.APPROVE_OPTION) {
                    String directoryPath = fileChooser.getSelectedFile().getPath();
                    JOptionPane.showMessageDialog(frame, "Selected Directory: " + directoryPath);
                }
            }
        });

        frame.getContentPane().add(selectDirectoryButton, BorderLayout.CENTER);
        frame.setVisible(true);
    }
}