1 /*
   2  * Copyright (c) 1997, 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.applet;
  27 
  28 import java.util.EventListener;
  29 import java.io.Serializable;
  30 import java.io.ObjectOutputStream;
  31 import java.io.IOException;
  32 
  33 /**
  34  * AppletEventMulticaster class.  This class manages an immutable
  35  * structure consisting of a chain of AppletListeners and is
  36  * responsible for dispatching events to them.
  37  *
  38  * @author  Sunita Mani
  39  *
  40  * @deprecated The Applet API is deprecated. See the
  41  * <a href="../../java/applet/package-summary.html"> java.applet package
  42  * documentation</a> for further information.
  43  */
  44 @Deprecated(since = "9")
  45 public class AppletEventMulticaster implements AppletListener {
  46 
  47     private final AppletListener a, b;
  48 
  49     public AppletEventMulticaster(AppletListener a, AppletListener b) {
  50         this.a = a; this.b = b;
  51     }
  52 
  53     public void appletStateChanged(AppletEvent e) {
  54         a.appletStateChanged(e);
  55         b.appletStateChanged(e);
  56     }
  57 
  58     /**
  59      * Adds Applet-listener-a with Applet-listener-b and
  60      * returns the resulting multicast listener.
  61      * @param a Applet-listener-a
  62      * @param b Applet-listener-b
  63      */
  64     public static AppletListener add(AppletListener a, AppletListener b) {
  65         return addInternal(a, b);
  66     }
  67 
  68     /**
  69      * Removes the old Applet-listener from Applet-listener-l and
  70      * returns the resulting multicast listener.
  71      * @param l Applet-listener-l
  72      * @param oldl the Applet-listener being removed
  73      */
  74     public static AppletListener remove(AppletListener l, AppletListener oldl) {
  75         return removeInternal(l, oldl);
  76     }
  77 
  78     /**
  79      * Returns the resulting multicast listener from adding listener-a
  80      * and listener-b together.
  81      * If listener-a is null, it returns listener-b;
  82      * If listener-b is null, it returns listener-a
  83      * If neither are null, then it creates and returns
  84      * a new AppletEventMulticaster instance which chains a with b.
  85      * @param a event listener-a
  86      * @param b event listener-b
  87      */
  88     private static AppletListener addInternal(AppletListener a, AppletListener b) {
  89         if (a == null)  return b;
  90         if (b == null)  return a;
  91         return new AppletEventMulticaster(a, b);
  92     }
  93 
  94 
  95     /**
  96      * Removes a listener from this multicaster and returns the
  97      * resulting multicast listener.
  98      * @param oldl the listener to be removed
  99      */
 100     protected AppletListener remove(AppletListener oldl) {
 101         if (oldl == a)  return b;
 102         if (oldl == b)  return a;
 103         AppletListener a2 = removeInternal(a, oldl);
 104         AppletListener b2 = removeInternal(b, oldl);
 105         if (a2 == a && b2 == b) {
 106             return this;        // it's not here
 107         }
 108         return addInternal(a2, b2);
 109     }
 110 
 111 
 112     /**
 113      * Returns the resulting multicast listener after removing the
 114      * old listener from listener-l.
 115      * If listener-l equals the old listener OR listener-l is null,
 116      * returns null.
 117      * Else if listener-l is an instance of AppletEventMulticaster
 118      * then it removes the old listener from it.
 119      * Else, returns listener l.
 120      * @param l the listener being removed from
 121      * @param oldl the listener being removed
 122      */
 123     private static AppletListener removeInternal(AppletListener l, AppletListener oldl) {
 124         if (l == oldl || l == null) {
 125             return null;
 126         } else if (l instanceof AppletEventMulticaster) {
 127             return ((AppletEventMulticaster)l).remove(oldl);
 128         } else {
 129             return l;           // it's not here
 130         }
 131     }
 132 }