J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 2003 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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 | } |