public static void main(String[] args) { // Sort the names based on their length, placing null first SortedSet<String> names = new TreeSet<>(Comparator.nullsFirst(Comparator.comparing(String::length))); names.add("HTML"); names.add("JAVA"); names.add("SQL"); names.add("CSS"); names.add(null); // Adds a null names.forEach(System.out::println); }