/**
 * Redistribution and use of this software and associated documentation ("Software"), with or
 * without modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain copyright statements and notices. Redistributions
 * must also contain a copy of this document.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of
 * conditions and the following disclaimer in the documentation and/or other materials provided with
 * the distribution.
 *
 * 3. The name "Exolab" must not be used to endorse or promote products derived from this Software
 * without prior written permission of Intalio, Inc. For written permission, please contact
 * info@exolab.org.
 *
 * 4. Products derived from this Software may not be called "Exolab" nor may "Exolab" appear in
 * their names without prior written permission of Intalio, Inc. Exolab is a registered trademark of
 * Intalio, Inc.
 *
 * 5. Due credit should be given to the Exolab Project (http://www.exolab.org/).
 *
 * THIS SOFTWARE IS PROVIDED BY INTALIO, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESSED OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
 * FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL INTALIO, INC. OR ITS
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
 * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Copyright 1999 (C) Intalio, Inc. All Rights Reserved.
 *
 * $Id$
 */

package org.exolab.castor.mapping;

import java.util.Enumeration;

/**
 * Collection handler for adding/listing elements of a collection. A collection field will use this
 * handler to add elements when it's value is set, and to enumerate then when it's value is
 * retrieved. A collection handler is instantiated only once, must be thread safe and not use any
 * synchronization.
 * 
 * @author <a href="arkin@intalio.com">Assaf Arkin</a>
 * @version $Revision$ $Date: 2003-03-03 00:05:44 -0700 (Mon, 03 Mar 2003) $
 */
public interface CollectionHandler<T> {

  /**
   * Add an object to the collection. A collection may not allow the same object to be added more
   * than once. The collection is provided as a parameter and is returned as the return value if the
   * returned collection is a different object. That way the handler can create a new collection or
   * change the collection as necessary (e.g. when resizing an array).
   * 
   * @param collection The collection, null if no collection has been created yet
   * @param object The object to add to the collection
   * @return The collection with the new object if a different instance than the <tt>collection</tt>
   *         parameter, null otherwise
   * @throws ClassCastException The collection handler does not support collections of this type
   */
  public Object add(Object collection, T object) throws ClassCastException;

  /**
   * Returns an enumeration of all the elements in the collection.
   * 
   * @param collection The collection
   * @return An enumeration of all the elements in the collection
   * @throws ClassCastException The collection handler does not support collections of this type
   */
  public Enumeration<T> elements(Object collection) throws ClassCastException;

  /**
   * Returns the number of elements in the collection.
   * 
   * @param collection The collection
   * @return Number of elements in the collection
   * @throws ClassCastException The collection handler does not support collections of this type
   */
  public int size(Object collection) throws ClassCastException;

  /**
   * Clears the collection of any objects. The collection is provided as a parameter and is returned
   * as the return value if the returned collection is a different object. That way the handler can
   * create a new collection or change the collection as necessary (e.g. when resizing an array).
   * 
   * @param collection The collection, null if no collection has been created yet
   * @return The empty collection if a different instance than the <tt>collection</tt> parameter,
   *         null otherwise
   * @throws ClassCastException The collection handler does not support collections of this type
   */
  public Object clear(Object collection) throws ClassCastException;

}
