gistfile1.txt

private static final Comparator<File> FILE_COMPARATOR = new Comparator<File>() {
            @Override
            public int compare(File lhs, File rhs) {
                boolean ldir = lhs.isDirectory();
                boolean rdir = rhs.isDirectory();

                if (ldir == rdir) {
                    // both are files or directories
                    return lhs.getName().compareToIgnoreCase(rhs.getName());
                } else if (ldir) {
                    return -1;
                } else {
                    return 1;
                }
            }
        };