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Message-ID: <42B827BC.10701@day.com>
Date: Tue, 21 Jun 2005 16:44:12 +0200
From: Felix Meschberger <Felix.Meschberger@day.com>
Organization: Day Software
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To: jackrabbit-dev@incubator.apache.org
Subject: Re: ObservationManager for JCR-RMI
References: <42B7CD44.3070700@day.com> <42B7EFA3.8050300@yukatan.fi>
 <42B806CA.1030502@day.com> <42B81F1D.7070309@zitting.name>
 <42B821B2.6050300@day.com> <42B8253F.5010105@zitting.name>
In-Reply-To: <42B8253F.5010105@zitting.name>
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Hi,

Hehe - those dreaded fingers are always faster than my mind ....

Next try. Hope this now makes it. Sorry for the overhead.

Regards
Felix

Jukka Zitting schrieb:

> Hi,
>
> Sorry to bug you, almost there... :-)
>
> Felix Meschberger wrote:
>
>>  * This software is the confidential and proprietary information of
>>  * Day Management AG, ("Confidential Information"). You shall not
>>  * disclose such Confidential Information and shall use it only in
>>  * accordance with the terms of the license agreement you entered into
>>  * with Day.
>
>
> BR,
>
> Jukka Zitting
>

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/*
 * Copyright 2004-2005 The Apache Software Foundation or its licensors,
 *                     as applicable.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.jackrabbit.rmi.observation;

import java.util.LinkedList;

/**
 * The <code>Queue</code> class is a very simple queue assuming that there is
 * at least one consumer and potentially multiple producers. This class poses
 * no restrictions on the size of the queue. 
 * 
 * @author Felix Meschberger
 */
public class Queue {

    /** The linked list implementing the queue of data */
    private final LinkedList queue;
    
    /**
     * Creates an instance of this queue.
     */
    public Queue() {
        queue = new LinkedList();
    }

    /**
     * Appends the given <code>object</code> to the end of the queue.
     * <p>
     * After appending the element, the queue is notified such that threads
     * waiting to retrieve an element from the queue are woken up.
     */
    public void put(Object object) {
        synchronized (queue) {
            queue.addLast(object);
            queue.notifyAll();
        }
    }

    /**
     * Returns the first element from the queue. If the queue is currently empty
     * the method waits at most the given number of milliseconds.
     * 
     * @param timeout The maximum number of milliseconds to wait for an entry in
     *      the queue if the queue is empty. If zero, the method waits forever
     *      for an element.
     * 
     * @return The first element of the queue or <code>null</code> if the method
     *      timed out waiting for an entry.
     * 
     * @throws InterruptedException Is thrown if the current thread is
     *      interrupted while waiting for the queue to get at least one entry.
     */
    public Object get(long timeout) throws InterruptedException {
        synchronized (queue) {
            // wait for data if the queue is empty
            if (queue.isEmpty()) {
                queue.wait(timeout);
            }
            
            // return null if queue is (still) empty
            if (queue.isEmpty()) {
                return null;
            }
            
            // return first if queue has content now
            return queue.removeFirst();
        }
    }
}

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