@Override
    public long remove(K key) {
        return complete(asyncCounterMap.remove(key));
    }
@Test
    public void testRemove() {
        atomicCounterMap.putIfAbsent(KEY1, VALUE1);
        assertThat(atomicCounterMap.size(), is(1));
        atomicCounterMap.remove(KEY1);
        assertThat(atomicCounterMap.size(), is(0));
    }