001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.net.util;
019
020import java.io.ObjectInputStream;
021import java.io.ObjectOutputStream;
022import java.io.Serializable;
023import java.util.EventListener;
024import java.util.Iterator;
025import java.util.concurrent.CopyOnWriteArrayList;
026
027/**
028 */
029
030public class ListenerList implements Serializable, Iterable<EventListener> {
031    private static final long serialVersionUID = -1934227607974228213L;
032
033    private final CopyOnWriteArrayList<EventListener> listeners;
034
035    public ListenerList() {
036        listeners = new CopyOnWriteArrayList<>();
037    }
038
039    public void addListener(final EventListener listener) {
040        listeners.add(listener);
041    }
042
043    public int getListenerCount() {
044        return listeners.size();
045    }
046
047    /**
048     * Return an {@link Iterator} for the {@link EventListener} instances.
049     *
050     * @return an {@link Iterator} for the {@link EventListener} instances
051     * @since 2.0 TODO Check that this is a good defensive strategy
052     */
053    @Override
054    public Iterator<EventListener> iterator() {
055        return listeners.iterator();
056    }
057
058    private void readObject(final ObjectInputStream in) {
059        throw new UnsupportedOperationException("Serialization is not supported");
060    }
061
062    /*
063     * Serialization is unnecessary for this class. Reject attempts to do so until such time as the Serializable attribute can be dropped.
064     */
065
066    public void removeListener(final EventListener listener) {
067        listeners.remove(listener);
068    }
069
070    private void writeObject(final ObjectOutputStream out) {
071        throw new UnsupportedOperationException("Serialization is not supported");
072    }
073
074}