class NaturalComparator implements Comparator<File> {
    public int compare(File f1, File f2) {
        String[] s1 = f1.getName().split("(?<=\\D)(?=\\d)|(?<=\\d)(?=\\D)"); // split *between* the transition from digits to non-digits & vica-versa
        String[] s2 = f2.getName().split("(?<=\\D)(?=\\d)|(?<=\\d)(?=\\D)");
        int c = 0;
        for (int i = 0; i < s1.length && i < s2.length; i++)
            try {
                c = new Long(s1[i]).compareTo(Long.parseLong(s2[i]));
            }
            catch (NumberFormatException nfe) {
                c = s1[i].compareTo(s2[i]);
            }
            finally {
                if (c != 0)
                    return c;
            }
        return s1.length > s2.length ? 1 : 0;
    }
}