public static List<List<String>> lfsort1(List<List<String>> list) {
        return lsort(
                lsort(list)
                        .stream()
                        .collect(groupingBy(List::size))
                        .values().stream().collect(toList()))
                .stream()
                .flatMap(Collection::stream)
                .collect(toList());
    }
(**) Sorting a list of lists according to length of sublists
java8/src/main/java/com/shekhargulati/ninetynine_problems/_01_lists/P28.java