/*
* Copyright 2003 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package sun.awt;
import java.lang.reflect.Array;
import java.util.EventListener;
/**
* A class that assists in managing {@link java.util.EventListener}s of
* the specified type. Its instance holds an array of listeners of the same
* type and allows to perform the typical operations on the listeners.
* This class is thread-safe.
*
* @author Alexander Gerasimov
*
* @since 1.5
*/
public class EventListenerAggregate {
private EventListener[] listenerList;
/**
* Constructs an <code>EventListenerAggregate</code> object.
*
* @param listenerClass the type of the listeners to be managed by this object
*
* @throws NullPointerException if <code>listenerClass</code> is
* <code>null</code>
* @throws ClassCastException if <code>listenerClass</code> is not
* assignable to <code>java.util.EventListener</code>
*/
public EventListenerAggregate(Class listenerClass) {
if (listenerClass == null) {
throw new NullPointerException("listener class is null");
}
if (!EventListener.class.isAssignableFrom(listenerClass)) {
throw new ClassCastException("listener class " + listenerClass +
" is not assignable to EventListener");
}
listenerList = (EventListener[])Array.newInstance(listenerClass, 0);
}
private Class getListenerClass() {
return listenerList.getClass().getComponentType();
}
/**
* Adds the listener to this aggregate.
*
* @param listener the listener to be added
*
* @throws ClassCastException if <code>listener</code> is not
* an instatce of <code>listenerClass</code> specified
* in the constructor
*/
public synchronized void add(EventListener listener) {
Class listenerClass = getListenerClass();
if (!listenerClass.isInstance(listener)) { // null is not an instance of any class
throw new ClassCastException("listener " + listener + " is not " +
"an instance of listener class " + listenerClass);
}
EventListener[] tmp = (EventListener[])Array.newInstance(listenerClass, listenerList.length + 1);
System.arraycopy(listenerList, 0, tmp, 0, listenerList.length);
tmp[listenerList.length] = listener;
listenerList = tmp;
}
/**
* Removes a listener that is equal to the given one from this aggregate.
* <code>equals()</code> method is used to compare listeners.
*
* @param listener the listener to be removed
*
* @return <code>true</code> if this aggregate contained the specified
* <code>listener</code>; <code>false</code> otherwise
*
* @throws ClassCastException if <code>listener</code> is not
* an instatce of <code>listenerClass</code> specified
* in the constructor
*/
public synchronized boolean remove(EventListener listener) {
Class listenerClass = getListenerClass();
if (!listenerClass.isInstance(listener)) { // null is not an instance of any class
throw new ClassCastException("listener " + listener + " is not " +
"an instance of listener class " + listenerClass);
}
for (int i = 0; i < listenerList.length; i++) {
if (listenerList[i].equals(listener)) {
EventListener[] tmp = (EventListener[])Array.newInstance(listenerClass,
listenerList.length - 1);
System.arraycopy(listenerList, 0, tmp, 0, i);
System.arraycopy(listenerList, i + 1, tmp, i, listenerList.length - i - 1);
listenerList = tmp;
return true;
}
}
return false;
}
/**
* Returns an array of all the listeners contained in this aggregate.
* The array is the data structure in which listeners are stored internally.
* The runtime type of the returned array is "array of <code>listenerClass</code>"
* (<code>listenerClass</code> has been specified as a parameter to
* the constructor of this class).
*
* @return all the listeners contained in this aggregate (an empty
* array if there are no listeners)
*/
public synchronized EventListener[] getListenersInternal() {
return listenerList;
}
/**
* Returns an array of all the listeners contained in this aggregate.
* The array is a copy of the data structure in which listeners are stored
* internally.
* The runtime type of the returned array is "array of <code>listenerClass</code>"
* (<code>listenerClass</code> has been specified as a parameter to
* the constructor of this class).
*
* @return a copy of all the listeners contained in this aggregate (an empty
* array if there are no listeners)
*/
public synchronized EventListener[] getListenersCopy() {
return (listenerList.length == 0) ? listenerList : (EventListener[])listenerList.clone();
}
/**
* Returns the number of lisetners in this aggregate.
*
* @return the number of lisetners in this aggregate
*/
public synchronized int size() {
return listenerList.length;
}
/**
* Returns <code>true</code> if this aggregate contains no listeners,
* <code>false</code> otherwise.
*
* @return <code>true</code> if this aggregate contains no listeners,
* <code>false</code> otherwise
*/
public synchronized boolean isEmpty() {
return listenerList.length == 0;
}
}