    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}