JEditorpane content not getting save in xsl format

Question

I am trying to save JEditorpane content, but it is not getting save. Where am I going wrong ?

Also I want the file to be saved as .xsl file . How can I achieve this ?

public class XSLTEditor {

    @SuppressWarnings("unused")
    private JFrame frame;

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                final JFrame f = new JFrame("XSLT Editor");
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                final JFileChooser fileChooser = new JFileChooser("C:\\xyz");

                JPanel gui = new JPanel(new BorderLayout());

                final JEditorPane document = new JEditorPane();
                JScrollPane scrollPane = new JScrollPane(document);
                gui.add(scrollPane, BorderLayout.CENTER);

                JButton save = new JButton("Save File");
                save.addActionListener(new ActionListener() {
                    public void actionPerformed(ActionEvent ae) {
                          String cmd = ((AbstractButton) ae.getSource()).getText();
                          try {
                              if (cmd.equals("Save")) {
                                FileWriter out = new FileWriter("C:\\Users\\Desktop\\JEditorPane.txt");
                                out.write(document.getText());
                                out.close();
                             }
                          } catch (Exception f) {
                             f.printStackTrace();
                          }
                    }
                });

                gui.add(save, BorderLayout.NORTH);
                f.setContentPane(gui);
                f.pack();
                f.setSize(400,400);
                f.setLocationByPlatform(true);

                f.setVisible(true);
            }
        });
    }
}

I am not including Open file chooser button function here in the code as I can successfully do that.