//    Copyright (C) 2002 -- See your tutor for details 
//
//    This library is free software; you can redistribute it and/or
//    modify it under the terms of the GNU Lesser General Public
//    License as published by the Free Software Foundation; either
//    version 2.1 of the License, or (at your option) any later version.
//

/**
 *  Circularly Linked implementation of a Queue ADT.
 *  @author Andrew H. Hoefel ahhoefel@student.math.uwaterloo.ca
 *  @version v0.5 -- Jan 5, 2002
 */
public class QueueCL extends Object implements Queue
{
   private Node tail = null;
   private int count = 0;

   public QueueCL()
   {  super();
   }

   public void enqueue(Object item)
   {  if(tail == null)
      {  this.tail = new Node(item);
         this.tail.setNext(tail);
      }else
      {  Node tempNode = new Node(item);
         tempNode.setNext(this.tail.getNext());
         this.tail.setNext(tempNode);
         this.tail = this.tail.getNext();
      }
      this.count++;
   }

   public Object dequeue()
   {  Object item = this.tail.getNext().getItem();
      if(tail.getNext() == tail)
      {  tail = null;
      }else
      {  this.tail.setNext(tail.getNext().getNext());
      }
      this.count--;
      return item;
   }

   public Object peek()
   {  return this.tail.getNext().getItem();
   }

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

   public int size()
   {  return count;
   }

}