1 /*
2 * Copyright (c) 2003, 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 listenerClass) {
57 if (listenerClass == null) {
58 throw new NullPointerException("listener class is null");
59 }
60
61 if (!EventListener.class.isAssignableFrom(listenerClass)) {
62 throw new ClassCastException("listener class " + listenerClass +
63 " is not assignable to EventListener");
64 }
65
66 listenerList = (EventListener[])Array.newInstance(listenerClass, 0);
67 }
68
69 private Class getListenerClass() {
70 return listenerList.getClass().getComponentType();
71 }
72
73 /**
74 * Adds the listener to this aggregate.
75 *
76 * @param listener the listener to be added
77 *
78 * @throws ClassCastException if <code>listener</code> is not
79 * an instatce of <code>listenerClass</code> specified
80 * in the constructor
81 */
82 public synchronized void add(EventListener listener) {
83 Class listenerClass = getListenerClass();
84
85 if (!listenerClass.isInstance(listener)) { // null is not an instance of any class
86 throw new ClassCastException("listener " + listener + " is not " +
87 "an instance of listener class " + listenerClass);
88 }
89
90 EventListener[] tmp = (EventListener[])Array.newInstance(listenerClass, listenerList.length + 1);
91 System.arraycopy(listenerList, 0, tmp, 0, listenerList.length);
92 tmp[listenerList.length] = listener;
93 listenerList = tmp;
94 }
95
96 /**
97 * Removes a listener that is equal to the given one from this aggregate.
98 * <code>equals()</code> method is used to compare listeners.
99 *
100 * @param listener the listener to be removed
101 *
102 * @return <code>true</code> if this aggregate contained the specified
103 * <code>listener</code>; <code>false</code> otherwise
104 *
105 * @throws ClassCastException if <code>listener</code> is not
106 * an instatce of <code>listenerClass</code> specified
107 * in the constructor
108 */
109 public synchronized boolean remove(EventListener listener) {
110 Class listenerClass = getListenerClass();
111
112 if (!listenerClass.isInstance(listener)) { // null is not an instance of any class
113 throw new ClassCastException("listener " + listener + " is not " +
114 "an instance of listener class " + listenerClass);
115 }
116
117 for (int i = 0; i < listenerList.length; i++) {
118 if (listenerList[i].equals(listener)) {
119 EventListener[] tmp = (EventListener[])Array.newInstance(listenerClass,
120 listenerList.length - 1);
121 System.arraycopy(listenerList, 0, tmp, 0, i);
122 System.arraycopy(listenerList, i + 1, tmp, i, listenerList.length - i - 1);
123 listenerList = tmp;
124
125 return true;
126 }
127 }
128
129 return false;
130 }
131
132 /**
133 * Returns an array of all the listeners contained in this aggregate.
134 * The array is the data structure in which listeners are stored internally.
135 * The runtime type of the returned array is "array of <code>listenerClass</code>"
136 * (<code>listenerClass</code> has been specified as a parameter to
137 * the constructor of this class).
138 *
139 * @return all the listeners contained in this aggregate (an empty
140 * array if there are no listeners)
141 */
142 public synchronized EventListener[] getListenersInternal() {
143 return listenerList;
144 }
145
146 /**
147 * Returns an array of all the listeners contained in this aggregate.
148 * The array is a copy of the data structure in which listeners are stored
149 * internally.
150 * The runtime type of the returned array is "array of <code>listenerClass</code>"
151 * (<code>listenerClass</code> has been specified as a parameter to
152 * the constructor of this class).
153 *
154 * @return a copy of all the listeners contained in this aggregate (an empty
155 * array if there are no listeners)
156 */
157 public synchronized EventListener[] getListenersCopy() {
158 return (listenerList.length == 0) ? listenerList : (EventListener[])listenerList.clone();
159 }
160
161 /**
162 * Returns the number of lisetners in this aggregate.
163 *
164 * @return the number of lisetners in this aggregate
165 */
166 public synchronized int size() {
167 return listenerList.length;
168 }
169
170 /**
171 * Returns <code>true</code> if this aggregate contains no listeners,
172 * <code>false</code> otherwise.
173 *
174 * @return <code>true</code> if this aggregate contains no listeners,
175 * <code>false</code> otherwise
176 */
177 public synchronized boolean isEmpty() {
178 return listenerList.length == 0;
179 }
180 }