/*
* Copyright (c) 1997, Oracle and/or its affiliates. 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. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package sun.applet;
import java.util.EventListener;
import java.io.Serializable;
import java.io.ObjectOutputStream;
import java.io.IOException;
/**
* AppletEventMulticaster class. This class manages an immutable
* structure consisting of a chain of AppletListeners and is
* responsible for dispatching events to them.
*
* @author Sunita Mani
*/
public class AppletEventMulticaster implements AppletListener {
private final AppletListener a, b;
public AppletEventMulticaster(AppletListener a, AppletListener b) {
this.a = a; this.b = b;
}
public void appletStateChanged(AppletEvent e) {
a.appletStateChanged(e);
b.appletStateChanged(e);
}
/**
* Adds Applet-listener-a with Applet-listener-b and
* returns the resulting multicast listener.
* @param a Applet-listener-a
* @param b Applet-listener-b
*/
public static AppletListener add(AppletListener a, AppletListener b) {
return addInternal(a, b);
}
/**
* Removes the old Applet-listener from Applet-listener-l and
* returns the resulting multicast listener.
* @param l Applet-listener-l
* @param oldl the Applet-listener being removed
*/
public static AppletListener remove(AppletListener l, AppletListener oldl) {
return removeInternal(l, oldl);
}
/**
* Returns the resulting multicast listener from adding listener-a
* and listener-b together.
* If listener-a is null, it returns listener-b;
* If listener-b is null, it returns listener-a
* If neither are null, then it creates and returns
* a new AppletEventMulticaster instance which chains a with b.
* @param a event listener-a
* @param b event listener-b
*/
private static AppletListener addInternal(AppletListener a, AppletListener b) {
if (a == null) return b;
if (b == null) return a;
return new AppletEventMulticaster(a, b);
}
/**
* Removes a listener from this multicaster and returns the
* resulting multicast listener.
* @param oldl the listener to be removed
*/
protected AppletListener remove(AppletListener oldl) {
if (oldl == a) return b;
if (oldl == b) return a;
AppletListener a2 = removeInternal(a, oldl);
AppletListener b2 = removeInternal(b, oldl);
if (a2 == a && b2 == b) {
return this; // it's not here
}
return addInternal(a2, b2);
}
/**
* Returns the resulting multicast listener after removing the
* old listener from listener-l.
* If listener-l equals the old listener OR listener-l is null,
* returns null.
* Else if listener-l is an instance of AppletEventMulticaster
* then it removes the old listener from it.
* Else, returns listener l.
* @param l the listener being removed from
* @param oldl the listener being removed
*/
private static AppletListener removeInternal(AppletListener l, AppletListener oldl) {
if (l == oldl || l == null) {
return null;
} else if (l instanceof AppletEventMulticaster) {
return ((AppletEventMulticaster)l).remove(oldl);
} else {
return l; // it's not here
}
}
}