public V remove(K key) {
        requireNonNull(key);
        long h = hash(key);
        return getSection(h).remove(key, null, (int) h);
    }
@Test
    public void testRemove() {
        ConcurrentOpenHashMap<String, String> map =
                ConcurrentOpenHashMap.<String, String>newBuilder().build();

        assertTrue(map.isEmpty());
        assertNull(map.put("1", "one"));
        assertFalse(map.isEmpty());

        assertFalse(map.remove("0", "zero"));
        assertFalse(map.remove("1", "uno"));

        assertFalse(map.isEmpty());
        assertTrue(map.remove("1", "one"));
        assertTrue(map.isEmpty());
    }