Retrieves, but does not remove, the head of the queue represented by
this deque (in other words, the first element of this deque), or
returns {@code null} if this deque is empty.
<p>This method is equivalent to {@link #peekFirst()}.
@return the head of the queue represented by this deque, or
{@code null} if this deque is empty
Retrieves, but does not remove, the head of the queue represented by this deque (in other words, the first element of this deque), or returns {@code null} if this deque is empty.
<p>This method is equivalent to {@link #peekFirst()}.
@return the head of the queue represented by this deque, or {@code null} if this deque is empty