### Question:
ConcurrentLongHashMap { public V putIfAbsent(long key, V value) { checkNotNull(value); long h = hash(key); return getSection(h).put(key, value, (int) h, true, null); } ConcurrentLongHashMap();  ConcurrentLongHashMap(int expectedItems);  ConcurrentLongHashMap(int expectedItems, int concurrencyLevel); long size(); long capacity(); boolean isEmpty(); V get(long key); boolean containsKey(long key); V put(long key, V value); V putIfAbsent(long key, V value); V computeIfAbsent(long key, LongFunction<V> provider); V remove(long key); boolean remove(long key, Object value); int removeIf(LongObjectPredicate<V> predicate); void clear(); void forEach(EntryProcessor<V> processor); List<Long> keys(); List<V> values();  }### Answer:
@Test public void testPutIfAbsent() { ConcurrentLongHashMap<String> map = new ConcurrentLongHashMap<>(); assertEquals(map.putIfAbsent(1, "one"), null); assertEquals(map.get(1), "one"); assertEquals(map.putIfAbsent(1, "uno"), "one"); assertEquals(map.get(1), "one"); }