/**
 * Base interface for queue implementations.
 */
public interface Queue {
	/**
	 * Returns true if queue has no elements
	 *
	 * @return 	true if the  queue has no elements
	 */
	public boolean isEmpty();


	/**
	 * Enqueues a new object to the queue
	 *
	 * @param x	Object to be enqueued into the queue.
	 */
	public void enqueue(Object x);


	/**
	 * Get the least recently inserted item in the queue.
	 * Does not alter the queue.
	 *
	 * @return 	The front of the queue.
	 * @exception	UnderflowException	Thrown if queue is empty.
	 */
	public Object peek();


	/**
	 * dequeues the front of the queue.
	 *
	 * @return 	The front of the queue.
	 * @exception	UnderflowException	Thrown if queue is empty.
	 */
	public Object dequeue();


	/**
	 * Erases all elements from the queue.
	 */
	public void makeEmpty();

}