Method enqueue

02Lab-Queues/RandomizedQueue.java:48–54

(Item item)

    // add the item
    public void enqueue(Item item) {
        if (item == null) throw new IllegalArgumentException();
        if (n == v.length) resize(2 * v.length);
        v[last++] = item;
        if (last == v.length) last = 0;
        n++;
    }

    // remove and return a random item
    public Item dequeue() {