package lists;

public class Queue implements ADTQueue
{
    private Node tail;
    private Node head;
    
    public Queue()
    {
        tail = null;
        head = null;
    }

    public Object dequeue()
    {
        Node p = head;
        if (head == tail)
        {
            head = null;
            tail = null;
        }
        else
        {
            head = head.getNext();
        }
        p.setNext(null);
        return p.getData();
    }


    public void enqueue(Object obj)
    {
        Node p = new Node(obj);
        if (head == null)
            head = p;    
        else
            tail.setNext(p);
        tail = p;
    }


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


    public Object peek()
    {
        return head.getData();
    }

}