@Override
        public E peek() {
            long currConsumerIndex;
            E e;
            do {
                currConsumerIndex = lvConsumerIndex();
                // other consumers may have grabbed the element, or queue might be empty
                e = lpElement(calcOffset(currConsumerIndex));
                // only return null if queue is empty
            } while (e == null && currConsumerIndex != producer.lvProducerIndex());
            return e;
        }
{@inheritDoc}
<p>
Because return null indicates queue is empty we cannot simply rely on next element visibility for poll and
must test producer index when next element is not visible.
jctools-experimental/src/main/java/org/jctools/queues/alt/MpscArrayConcurrentQueue.java