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Java > Open Source Codes > com > db4o > events > impl > Event4Impl


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.events.impl;
22
23 import com.db4o.events.*;
24 import com.db4o.foundation.*;
25
26 /**
27  * @exclude
28  * @sharpen.ignore
29  */
30 public class Event4Impl implements Event4 {
31
32     private Collection4 _listeners;
33     
34     public void addListener(EventListener4 listener) {
35         validateListener(listener);
36         
37         if (null == _listeners) {
38             _listeners = new Collection4();
39         }
40         _listeners.add(listener);
41     }
42
43     public void removeListener(EventListener4 listener) {
44         validateListener(listener);
45         
46         if (null != _listeners) {
47             _listeners.remove(listener);
48             if (0 == _listeners.size()) {
49                 _listeners = null;
50             }
51         }
52     }
53     
54     public void trigger(EventArgs args) {
55         if (null == _listeners) {
56             return;
57         }
58         
59         Iterator4 iterator = _listeners.iterator();
60         while (iterator.moveNext()) {
61             ((EventListener4)iterator.current()).onEvent(this, args);
62         }
63     }
64     
65     private void validateListener(EventListener4 listener) {
66         if (null == listener) {
67             throw new ArgumentNullException("listener");
68         }
69     }
70 }
71
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