/* This file is part of the db4o object database http://www.db4o.com
Copyright (C) 2004 - 2011 Versant Corporation http://www.versant.com
db4o is free software; you can redistribute it and/or modify it under
the terms of version 3 of the GNU General Public License as published
by the Free Software Foundation.
db4o 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
for more details.
You should have received a copy of the GNU General Public License along
with this program. If not, see http://www.gnu.org/licenses/. */
package com.db4o.internal.events;
import com.db4o.events.*;
import com.db4o.foundation.*;
/**
* @exclude
* @sharpen.ignore
*
* @sharpen.macro System.EventHandler<$T>
*/
public class Event4Impl<T extends EventArgs> implements Event4<T> {
/**
* @sharpen.remove null
*/
public static <T extends EventArgs> Event4Impl<T> newInstance() {
return new Event4Impl();
}
private Collection4 _listeners;
protected Event4Impl() {
}
public final void addListener(EventListener4<T> listener) {
validateListener(listener);
Collection4 listeners = new Collection4();
listeners.add(listener);
if (null != _listeners) {
listeners.addAll(_listeners);
}
_listeners = listeners;
onListenerAdded();
}
private Collection4 copyListeners() {
return null != _listeners
? new Collection4(_listeners)
: new Collection4();
}
/**
* Might be overridden whenever specific events need
* to know when listeners subscribe to the event.
*/
protected void onListenerAdded() {
}
public final void removeListener(EventListener4<T> listener) {
validateListener(listener);
if (null == _listeners) {
return;
}
Collection4 listeners = copyListeners();
listeners.remove(listener);
_listeners = listeners;
}
/**
* @sharpen.macro if (null != $expression) $expression(null, $arguments)
*/
public final void trigger(T args) {
if (null == _listeners) {
return;
}
Iterator4 iterator = _listeners.iterator();
while (iterator.moveNext()) {
EventListener4<T> listener = (EventListener4<T>)iterator.current();
listener.onEvent(this, args);
}
}
private void validateListener(EventListener4<T> listener) {
if (null == listener) {
throw new ArgumentNullException();
}
}
/**
* @sharpen.macro ($expression != null)
*/
public boolean hasListeners() {
return _listeners != null;
}
}