package Queue;

import java.util.*;

/**
 * Interface UniqueQueue builds on Queue by having the capability
 * to remove a specified item from the middle of the queue.
 * One can quickly test if an item is inside the queue.
 * A restriction is that one cannot insert the same item multiple
 * times into the queue.
 *
 * @see Queue.Queue
 *
 * @author Thomas Wang
 * @version 0.55
 */
public abstract interface UniqueQueue extends Queue
{
  /**
   * Returns true if the specified element is inside the queue.
   * False is returned otherwise.
   *
   * @param element the specified element
   * @return true or false
   */
  public boolean isInside(Object element);

  /**
   * Remove the specified element from the queue.  If the element
   * is not inside the queue, then exception NoSuchElementException
   * will be thrown.
   *
   * @param element the specified element
   * @exception NoSuchElementException thrown when specified element
   * is not inside the queue.
   */
  public void removeElement(Object element)
    throws NoSuchElementException;
}