/** Source code example for "A Practical Introduction to Data
    Structures and Algorithm Analysis, 3rd Edition (Java)" 
    by Clifford A. Shaffer
    Copyright 2008-2011 by Clifford A. Shaffer
*/

/** Queue ADT */
public interface Queue<E> {

  /** Reinitialize the queue.  The user is responsible for
      reclaiming the storage used by the queue elements. */
  public void clear();

  /** Place an element at the rear of the queue.
      @param it The element being enqueued. */
  public void enqueue(E it);

  /** Remove and return element at the front of the queue.
      @return The element at the front of the queue. */
  public E dequeue();

  /** @return The front element. */
  public E frontValue();

  /** @return The number of elements in the queue. */
  public int length();
}