Retrieves and removes the first element of this deque. This method
differs from {@link #pollFirst pollFirst} only in that it throws an
exception if this deque is empty.
@return the head of this deque
@throws NoSuchElementException if this deque is empty
Retrieves and removes the first element of this deque. This method differs from {@link #pollFirst pollFirst} only in that it throws an exception if this deque is empty.
@return the head of this deque @throws NoSuchElementException if this deque is empty