Retrieves, but does not remove, the first element of this deque.
This method differs from {@link #peekFirst peekFirst} 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
See Implementation
Retrieves, but does not remove, the first element of this deque.
This method differs from {@link #peekFirst peekFirst} 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