1 /*
2 * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package sun.awt;
27
28 import java.lang.reflect.Array;
29 import java.util.EventListener;
30
31
32 /**
33 * A class that assists in managing {@link java.util.EventListener}s of
34 * the specified type. Its instance holds an array of listeners of the same
35 * type and allows to perform the typical operations on the listeners.
36 * This class is thread-safe.
37 *
38 * @author Alexander Gerasimov
39 *
40 * @since 1.5
41 */
42 public class EventListenerAggregate {
43
44 private EventListener[] listenerList;
45
46 /**
47 * Constructs an <code>EventListenerAggregate</code> object.
48 *
49 * @param listenerClass the type of the listeners to be managed by this object
50 *
51 * @throws NullPointerException if <code>listenerClass</code> is
52 * <code>null</code>
53 * @throws ClassCastException if <code>listenerClass</code> is not
54 * assignable to <code>java.util.EventListener</code>
55 */
56 public EventListenerAggregate(Class<? extends EventListener> listenerClass) {
57 if (listenerClass == null) {
58 throw new NullPointerException("listener class is null");
59 }
60
61 listenerList = (EventListener[])Array.newInstance(listenerClass, 0);
62 }
63
64 private Class<?> getListenerClass() {
65 return listenerList.getClass().getComponentType();
66 }
67
68 /**
69 * Adds the listener to this aggregate.
70 *
71 * @param listener the listener to be added
72 *
73 * @throws ClassCastException if <code>listener</code> is not
74 * an instatce of <code>listenerClass</code> specified
75 * in the constructor
76 */
77 public synchronized void add(EventListener listener) {
78 Class<?> listenerClass = getListenerClass();
79
80 if (!listenerClass.isInstance(listener)) { // null is not an instance of any class
81 throw new ClassCastException("listener " + listener + " is not " +
82 "an instance of listener class " + listenerClass);
83 }
84
85 EventListener[] tmp = (EventListener[])Array.newInstance(listenerClass, listenerList.length + 1);
86 System.arraycopy(listenerList, 0, tmp, 0, listenerList.length);
87 tmp[listenerList.length] = listener;
88 listenerList = tmp;
89 }
90
91 /**
92 * Removes a listener that is equal to the given one from this aggregate.
93 * <code>equals()</code> method is used to compare listeners.
94 *
95 * @param listener the listener to be removed
96 *
97 * @return <code>true</code> if this aggregate contained the specified
98 * <code>listener</code>; <code>false</code> otherwise
99 *
100 * @throws ClassCastException if <code>listener</code> is not
101 * an instatce of <code>listenerClass</code> specified
102 * in the constructor
103 */
104 public synchronized boolean remove(EventListener listener) {
105 Class<?> listenerClass = getListenerClass();
106
107 if (!listenerClass.isInstance(listener)) { // null is not an instance of any class
108 throw new ClassCastException("listener " + listener + " is not " +
109 "an instance of listener class " + listenerClass);
110 }
111
112 for (int i = 0; i < listenerList.length; i++) {
113 if (listenerList[i].equals(listener)) {
114 EventListener[] tmp = (EventListener[])Array.newInstance(listenerClass,
115 listenerList.length - 1);
116 System.arraycopy(listenerList, 0, tmp, 0, i);
117 System.arraycopy(listenerList, i + 1, tmp, i, listenerList.length - i - 1);
118 listenerList = tmp;
119
120 return true;
121 }
122 }
123
124 return false;
125 }
126
127 /**
128 * Returns an array of all the listeners contained in this aggregate.
129 * The array is the data structure in which listeners are stored internally.
130 * The runtime type of the returned array is "array of <code>listenerClass</code>"
131 * (<code>listenerClass</code> has been specified as a parameter to
132 * the constructor of this class).
133 *
134 * @return all the listeners contained in this aggregate (an empty
135 * array if there are no listeners)
136 */
137 public synchronized EventListener[] getListenersInternal() {
138 return listenerList;
139 }
140
141 /**
142 * Returns an array of all the listeners contained in this aggregate.
143 * The array is a copy of the data structure in which listeners are stored
144 * internally.
145 * The runtime type of the returned array is "array of <code>listenerClass</code>"
146 * (<code>listenerClass</code> has been specified as a parameter to
147 * the constructor of this class).
148 *
149 * @return a copy of all the listeners contained in this aggregate (an empty
150 * array if there are no listeners)
151 */
152 public synchronized EventListener[] getListenersCopy() {
153 return (listenerList.length == 0) ? listenerList : listenerList.clone();
154 }
155
156 /**
157 * Returns the number of lisetners in this aggregate.
158 *
159 * @return the number of lisetners in this aggregate
160 */
161 public synchronized int size() {
162 return listenerList.length;
163 }
164
165 /**
166 * Returns <code>true</code> if this aggregate contains no listeners,
167 * <code>false</code> otherwise.
168 *
169 * @return <code>true</code> if this aggregate contains no listeners,
170 * <code>false</code> otherwise
171 */
172 public synchronized boolean isEmpty() {
173 return listenerList.length == 0;
174 }
175 }