Ochered

class QueueY<Item> implements Iterable<Item> {
    private QueObj<Item> head;
    private QueObj<Item> tail;
    private int size;

    private static class QueObj<Item> {
        Item value;
        QueObj next;

        QueObj(Item value, QueObj next) {
            this.value = value;
            this.next = next;
        }
    }

    private class QueueIterator implements Iterator<Item> {
        QueObj current = head;

        @Override
        public boolean hasNext() {
            return (current != null);
        }

        @Override
        public Item next() {
            if (hasNext()) {
                QueObj<Item> item = current;
                current = item.next;
                return item.value;
            }
            return null;
        }
    }

    @Override
    public Iterator<Item> iterator() {
        return new QueueIterator();
    }

    public boolean isEmpty() {
        return (head == null);
    }

    public int size() {
        return size;
    }

    public void Enqueue(Item value)
    {
        if (isEmpty()) {
            tail = head = new QueObj<Item>(value, null);
            size++;
        }
        else
        {
            QueObj item = new QueObj (value, null );
            tail.next = item;
            tail = item;
            size++;
        }
    }

    public Item Dequeue()
    {
        Item result = head.value;
        head = head.next;
        if (head == null)
            tail = null;
        size--;
        return result;
    }
}