queue main()

public static void main(String[] args) {
    /* Queue demo */
    Queue<Integer> queue = new Queue<>();

    queue.enqueue(1);
    queue.enqueue(2);
    queue.enqueue(3);

    System.out.println("Queue demo: ");
    System.out.println("peek: " + queue.peek());
    System.out.println(queue.dequeue());
    System.out.println(queue.dequeue());
    System.out.println(queue.dequeue());
    queue.enqueue(4);

    System.out.println("queue size: " + queue.size());
}