public E poll() {
    return pollFirst();
  }
Retrieves and removes the head of the queue represented by this deque.
This method differs from {@link #poll poll} only in that it throws an
exception if this deque is empty.
<br>
This method is equivalent to {@link #removeFirst() removeFirst}.

@return the head of the queue represented by this deque
@throws NoSuchElementException if this deque is empty
llap-server/src/java/org/apache/hadoop/hive/llap/daemon/impl/PriorityBlockingDeque.java