/*
 * Generic Queue Interface
 * $Id: Queue.java,v 1.1.1.1 2002/06/05 21:56:32 root Exp $
 *
 * Developed for "Rethinking CS101", a project of Lynn Andrea Stein's AP Group.
 * For more information, see <a href="http://www.ai.mit.edu/projects/cs101/">the
 * CS101 homepage</a> or email <las@ai.mit.edu>.
 *
 * Copyright (C) 1998 Massachusetts Institute of Technology.
 * Please do not redistribute without obtaining permission.
 */

package cs101.util.queue;

import java.util.Enumeration;

/**
 * Generic Queue Interface.  Allows insertion/deletion at either end.
 * <p>
 * Copyright (c) 1998 Massachusetts Institute of Technology 
 *
 * @author Todd C. Parnell, tparnell@ai.mit.edu
 * @version $Id: Queue.java,v 1.1.1.1 2002/06/05 21:56:32 root Exp $
 */
public interface Queue {

  public static final int FRONT = 0;
  public static final int BACK  = 1;

  /** Returns the number of elements in this. */
  public int size();

  /**
   * Gets the tail object from the queue </B>without</B> removing
   * it. 
   */
  public Object peek();

  /**
   * Gets the object from the specified end of the queue
   * </B>without</B> removing it. 
   */
  public Object peek(int end);

  /** Puts obj into the front the queue. */
  public void enqueue(Object obj);

  /** Puts obj into the specified end of the queue. */
  public void enqueue(Object obj, int end);

  /** Removes and returns the Object at the tail of the queue. */
  public Object dequeue();

  /** Removes and returns the Object at the specified end of the queue. */
  public Object dequeue(int end);

  /** Tests whether the queue is empty. */
  public boolean isEmpty ();

  /** Returns an Enumeration of the Objects in the queue.<p> 
   *
   * <I>Note: Do not modify the queue while enumerating--unpredictable
   * behavior may result.</I>
   *
   * @see java.util.Enumeration
   */
  public Enumeration elements();
      
}

/*
 * $Log: Queue.java,v $
 * Revision 1.1.1.1  2002/06/05 21:56:32  root
 * CS101 comes to Olin finally.
 *
 * Revision 1.1  2000/04/24 22:17:18  nathanw
 * Bulk reorganization
 *
 * Revision 1.12  1999/07/27 16:59:16  las
 * Updated cs101.util.Queue.java to spell its method peek()
 *
 * Revision 1.11  1999/01/21 20:49:19  tparnell
 * Made Queue.java an interface and added DefaultQueue.java as an implementation.
 *
 * Revision 1.10  1998/07/31 21:42:36  tparnell
 * bugfix
 *
 * Revision 1.9  1998/07/31 21:39:01  tparnell
 * added size() method
 *
 * Revision 1.8  1998/07/24 17:19:33  tparnell
 * Placate new javadoc behavior
 *
 */