public class ArrayPureQueue<E> implements PureQueue<E> // Note: does not implement Collection<E>
{
	protected E [ ] data;

	protected int size,
                      head,
                      tail;
	
	/**
	 *  Determines the number of elements in this PureQueue object.
	 *
	 *  @return the number of elements in this PureQueue object.
	 *
	 */
	public int size()
	{
		
	}


	/**
	 *  Determines if this PureQueue object has no elements.
	 *
	 *  @return true - if this PureQueue object has no elements; otherwise,
	 *                          return false.
	 *
	 */
	public boolean isEmpty()
	{
		
	}
		
		 
	/**
	 *  Inserts a specified element at the back of this PureQueue object.
	 *  The averageTime(n) is constant and worstTime(n) is O(n).
	 *  
	 *  @param element - the element to be appended.
	 *
	 */
        public void enqueue (E element)
	{
		if (size == data.length) 
        	{
            		// double the length of data
            		E [ ] oldData = data;
            		data = (E [ ]) new Object [data.length * 2];

            		// copy oldData [head...oldData.length-1] to data [0...oldData.length-1 - head]
            		System.arraycopy (oldData, head, data, 0, oldData.length - head);

            		if (head > 0)

                		// copy oldData [0...tail] to data [oldData.length - head...oldData.length-1]
                		System.arraycopy (oldData, 0, data, oldData.length - head, tail+1);

            		head = 0;
            		tail = oldData.length - 1;		
        	} // if this ArrayPureQueue object occupies all of data
        	tail = (tail + 1) % data.length;
        	size++;
        	data [tail] = element;	
    	} // method enqueue


	/**
	 *  Removes the front element from this PureQueue object.
	 *  
	 *  @return - the element removed.
	 *  
	 *  @throws NoSuchElementException - if this PureQueue object is empty.
	 *
	 */ 
	public E dequeue()
	{
		
	}

	/**
	 *  Returns the front element in this PureQueue object.
	 *  
	 *  @return - the element returned.
	 *  
	 *  @throws NoSuchElementException - if this PureQueue object is empty.
	 *
	 */		
	public E front()
	{
		
	}

} // class ArrayPureQueue