@Test public void solution() throws Exception { ConcurrentHashMap<String, Long> map = new ConcurrentHashMap<>(); TextReader.getWordsFromFile("/alice.txt") .stream() .forEach(w -> map.computeIfAbsent(w, k -> (long) k.length())); Map.Entry<String, Long> entry = map.reduceEntries( Runtime.getRuntime().availableProcessors(), (v1, v2) -> v1.getValue() > v2.getValue() ? v1 : v2); assertThat(entry.getKey()).isEqualTo("unenforceability"); }