/*

  * 

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

  * 

  * Copyright 2007-2008 Sun Microsystems, Inc. All rights reserved.

  * 

  * The contents of this file are subject to the terms of either the GNU

  * General Public License Version 2 only ("GPL") or the Common Development

  * and Distribution License("CDDL") (collectively, the "License").  You

  * may not use this file except in compliance with the License. You can obtain

  * a copy of the License at https://glassfish.dev.java.net/public/CDDL+GPL.html

  * or glassfish/bootstrap/legal/LICENSE.txt.  See the License for the specific

  * language governing permissions and limitations under the License.

  * 

  * When distributing the software, include this License Header Notice in each

  * file and include the License file at glassfish/bootstrap/legal/LICENSE.txt.

  * Sun designates this particular file as subject to the "Classpath" exception

  * as provided by Sun in the GPL Version 2 section of the License file that

  * accompanied this code.  If applicable, add the following below the License

  * Header, with the fields enclosed by brackets [] replaced by your own

  * identifying information: "Portions Copyrighted [year]

  * [name of copyright owner]"

  * 

  * Contributor(s):

  * 

  * If you wish your version of this file to be governed by only the CDDL or

  * only the GPL Version 2, indicate your decision by adding "[Contributor]

  * elects to include this software in this distribution under the [CDDL or GPL

  * Version 2] license."  If you don't indicate a single choice of license, a

  * recipient has the option to distribute your version of this file under

  * either the CDDL, the GPL Version 2 or to extend the choice of license to

  * its licensees as provided above.  However, if you add GPL Version 2 code

  * and therefore, elected the GPL Version 2 license, then the option applies

  * only if the new code is made subject to such option by the copyright

  * holder.

  *

  */

 package com.sun.grizzly.util;

 import java.util.concurrent.ConcurrentLinkedQueue;

 /**

  * <code>ObjectPool</code> implementation based on {@link ConcurrentLinkedQueue}

  * 

  * @author Alexey Stashok

  */

 public abstract class ConcurrentLinkedQueuePool<E> implements ObjectPool<E> {

     private volatile ConcurrentLinkedQueue<E> pool;

     public abstract E newInstance();

     public E poll() {

         if (pool == null) {

             synchronized(this) {

                 if (pool == null) {

                     pool = new ConcurrentLinkedQueue<E>();

                 }

             }

         }

         E object = pool.poll();

         if (object == null) {

             object = newInstance();

         }

         return object;

     }

     public void offer(E object) {

         if (pool != null) {

             pool.offer(object);

         }

     }

 }