Queue: Enqueue

Task: Add three values to the queue

Queue<Integer> q = new ArrayDeque<>(); q.offer(v);   // enqueue: join at the rearq.peek();     // read the front, leave it thereq.poll();     // dequeue: take from the frontq.size();     // how many are waiting

What you are watching

Enqueueing adds a value at the rear, and the rear is the only place anything can join. 12, then 27, then 5: each one lines up behind the one before it and none of them can overtake. 12 arrived first, so 12 is at the front and will be the first to leave - the order values arrive in is the order they will go out in.