public void saveToFile() {
    FileDialog fileDialog = new FileDialog(this, "Save to File", FileDialog.SAVE);
    fileDialog.setFilenameFilter(new FilenameFilter() {
                    public boolean accept(File dir, String name) {
                        return  name.length() > 4 &&
                            name.substring(name.length()-4).equals(".spr");
                    }
                });
    fileDialog.setVisible(true);
    File[] files = fileDialog.getFiles();

    if (files.length != 0) {
        String path = files[0].getCanonicalPath();
        if (!path.substring(path.length()-4).equals(".spr"))
            path = path + ".spr";

        try {
            File fout = new File(path);
            // write to the file
        } catch (Exception e) {
            e.printStackTrace();
            JOptionPane.showMessageDialog(this, "Error saving file!", "Error", JOptionPane.ERROR_MESSAGE);
        }
    }
}