@Override
    public boolean containsKey(final Object key)
    {
        final int mask = values.length - 1;
        int index = Hashing.hash(key, mask);

        boolean found = false;
        while (missingValue != values[index])
        {
            if (key.equals(keys[index]))
            {
                found = true;
                break;
            }

            index = ++index & mask;
        }

        return found;
    }
@Test
    public void shouldNotContainKeyOfAMissingKey() {
        assertFalse(map.containsKey("1"));
    }