/*
 *                 Sun Public License Notice
 * 
 * The contents of this file are subject to the Sun Public License
 * Version 1.0 (the "License"). You may not use this file except in
 * compliance with the License. A copy of the License is available at
 * http://www.sun.com/
 * 
 * The Original Code is NetBeans. The Initial Developer of the Original
 * Code is Sun Microsystems, Inc. Portions Copyright 1997-2004 Sun
 * Microsystems, Inc. All Rights Reserved.
 */

package org.openide.util.enum;

import java.util.Enumeration;
import java.util.NoSuchElementException;

/**
 * Enumeration that represents a queue. It allows by redefining
 * method process each outputed object to add other to the end of
 * queue of waiting objects by a call to put.
 * @deprecated JDK 1.5 treats enum as a keyword so this class was
 *             replaced by {@link org.openide.util.Enumerations#queue}.
 * @author Jaroslav Tulach, Petr Hamernik
 */
public class QueueEnumeration extends Object implements Enumeration {
    /** item in linked list of Objects */
    private static final class ListItem {
        Object object;
        ListItem next;

        /** @param o the object for this item */
        ListItem (Object o) {
            object = o;
        }
    }
    /** next object to be returned */
    private ListItem next = null;
    /** last object in the queue */
    private ListItem last = null;

    /** Processes object before it is returned from nextElement method.
    * This method allows to add other object to the end of the queue
    * by a call to put method. This implementation does
    * nothing.
    *
    * @see #put
    * @param o the object to be processed
    */
    protected void process (Object o) {
    }

    /** Put adds new object to the end of queue.
    * @param o the object to add
    */
    public synchronized void put (Object o) {
        if (last != null) {
            ListItem li = new ListItem (o);
            last.next = li;
            last = li;
        } else {
            next = last = new ListItem (o);
        }
    }

    /** Adds array of objects into the queue.
    * @param arr array of objects to put into the queue
    */
    public synchronized void put (Object[] arr) {
        for (int i = 0; i < arr.length; i++) {
            put (arr[i]);
        }
    }

    /** Is there any next object?
    * @return true if there is next object, false otherwise
    */
    public boolean hasMoreElements () {
        return next != null;
    }

    /** @return next object in enumeration
    * @exception NoSuchElementException if there is no next object
    */
    public synchronized Object nextElement () {
        if (next == null) {
            throw new NoSuchElementException ();
        }
        Object res = next.object;

        if ((next = next.next) == null) {
            last = null;
        };
        process(res);
        return res;
    }
}