public static List<String> bigSorting(List<String> unsorted) {
    Map<Integer, List<String>> map = unsorted.stream().collect(Collectors.groupingBy(String::length));
    List<String> result = new ArrayList<>();
    map.keySet().stream().sorted().forEach(key -> {
        List<String> r = map.get(key);
        r.sort((s1, s2) -> s1.compareTo(s2));
        result.addAll(r);
    });
    return result;
}