private int N;              
    private Node<object> first;    
    private Node<object> last;     

    private static class Node<object> {
        private object object;
        private Node<object> next;
    }

    /**
     * Initializes an empty queue.
     */
    public queue() {
        first = null;
        last  = null;
        N = 0;
    }

    public boolean isEmpty() {
        return first == null;
    }
    public int size() {
        return N;     
    }
    public object three() {
        return first.object;
    }

    public void one(object item) {
        Node<object> oldlast = last;
        last = new Node<object>();
        last.object = item;
        last.next = null;
        if (isEmpty())
            first = last;
        else     
            oldlast.next = last;
        N++;
    }
    public object two() {
        object item = first.object;
        first = first.next;
        N--;
        if (isEmpty())
            last = null;  
        return item;
    }
}