Queue<Integer> queue = new LinkedList<>();
queue.offer(1) // [1] O(1)
queue.offer(2) // [1, 2]
queue.offer(3) // [1, 2, 3]
int peek = queue.peek() // [1, 2, 3] peek = 1, [1, 2, 3] O(1)
int peekElement = queue.poll() // peekElement == 1, [2, 3] O(1)