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Java > Open Source Codes > org > openide > filesystems > ListenerList


1 /*
2  * The contents of this file are subject to the terms of the Common Development
3  * and Distribution License (the License). You may not use this file except in
4  * compliance with the License.
5  *
6  * You can obtain a copy of the License at http://www.netbeans.org/cddl.html
7  * or http://www.netbeans.org/cddl.txt.
8  *
9  * When distributing Covered Code, include this CDDL Header Notice in each file
10  * and include the License file at http://www.netbeans.org/cddl.txt.
11  * If applicable, add the following below the CDDL Header, with the fields
12  * enclosed by brackets [] replaced by your own identifying information:
13  * "Portions Copyrighted [year] [name of copyright owner]"
14  *
15  * The Original Software is NetBeans. The Initial Developer of the Original
16  * Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
17  * Microsystems, Inc. All Rights Reserved.
18  */
19
20 package org.openide.filesystems;
21
22 import java.util.ArrayList JavaDoc;
23 import java.util.Collections JavaDoc;
24 import java.util.List JavaDoc;
25
26 /**
27  * A class that holds a list of listeners of some type.
28  * Replacement of EventListListener, that solves performance issue #20715
29  * @author rm111737
30  */
31 class ListenerList<T> {
32     private final List JavaDoc<T> listenerList;
33     private List JavaDoc<T> copy = null;
34
35     ListenerList() {
36         listenerList = new ArrayList JavaDoc<T>();
37     }
38
39     /**
40      * Adds the listener .
41      **/
42     public synchronized boolean add(T listener) {
43         if (listener == null) {
44             throw new NullPointerException JavaDoc();
45         }
46
47         copy = null;
48
49         return listenerList.add(listener);
50     }
51
52     /**
53      * Removes the listener .
54      **/
55     public synchronized boolean remove(T listener) {
56         copy = null;
57
58         return listenerList.remove(listener);
59     }
60
61     /**
62      * Passes back the event listener list
63      */
64     public synchronized List JavaDoc<T> getAllListeners() {
65         if (copy == null) {
66             copy = new ArrayList JavaDoc<T>(listenerList);
67         }
68         return copy;
69     }
70     
71     public synchronized boolean hasListeners() {
72         return !listenerList.isEmpty();
73     }
74     
75 }
76
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