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1   /*
2    * This file is part of Domingo
3    * an Open Source Java-API to Lotus Notes/Domino
4    * hosted at http://domingo.sourceforge.net
5    *
6    * Copyright (c) 2003-2007 Beck et al. projects GmbH Munich, Germany (http://www.bea.de)
7    *
8    * This library is free software; you can redistribute it and/or
9    * modify it under the terms of the GNU Lesser General Public
10   * License as published by the Free Software Foundation; either
11   * version 2.1 of the License, or (at your option) any later version.
12   *
13   * This library is distributed in the hope that it will be useful,
14   * but WITHOUT ANY WARRANTY; without even the implied warranty of
15   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16   * Lesser General Public License for more details.
17   *
18   * You should have received a copy of the GNU Lesser General Public
19   * License along with this library; if not, write to the Free Software
20   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
21   */
22  
23  package de.bea.domingo.queue;
24  
25  /***
26   * Interface definition of a general Queue.
27   *
28   * @author <a href="mailto:kriede@users.sourceforge.net">Kurt Riede</a>
29   */
30  public interface Queue {
31  
32      /***
33       * Returns the number of objects in the queue.
34       *
35       * @return number of objects in the queue
36       */
37      int size();
38  
39      /***
40       * Checks is the queue is empty or not.
41       *
42       * @return <code>true</code> if the queue is empty, else <code>false</code>
43       */
44      boolean isEmpty();
45  
46      /***
47       * Enqueues an object to the queue.
48       *
49       * @param obj the object to enqueue
50       */
51      void enqueue(Object obj);
52  
53      /***
54       * Dequeues an object from the queue.
55       *
56       * @return next object from the queue
57       *         or <code>null</code> if the queue is empty
58       */
59      Object dequeue();
60  }