public class Queue
{
	private QueueNode head, tail;
	
	public void enqueue(Object data)
	{
		if(head == null)
		{
			head = new QueueNode(null, data);
		    tail = head;
		}
		else
		{
			head.setPrevious(new QueueNode(null, data));
			head = head.getPrevious();
		}
	}
	
	public Object dequeue()
	{
		QueueNode temp = tail;
		tail = tail.getPrevious();		
		return temp.getData();
	}
	
	public Object peekFront()
	{
		return tail.getData();
	}
	
	public boolean isEmpty()
	{
		return tail == null;
	}
}