// "Replace with forEach" "true" import java.util.*; public class Main { private Map<Integer, Map<Integer, List<String>>> test(String... list) { Map<Integer, Map<Integer, List<String>>> map = new HashMap<>(); Arrays.stream(list).filter(Objects::nonNull).forEach(s -> map.computeIfAbsent(s.length(), k -> new HashMap<>()).computeIfAbsent(s.length(), k -> new ArrayList<>()).add(s)); return map; } }