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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.harmony.awt;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collections;
import java.util.EventListener;
import java.util.Iterator;
import java.util.List;
/**
* List of AWT listeners. It is for 3 purposes.
* 1. To support list modification from listeners
* 2. To ensure call for all listeners as atomic operation
* 3. To support system listeners that are needed for built-in AWT components
*/
public class ListenerList<T extends EventListener> implements Serializable {
private static final long serialVersionUID = 9180703263299648154L;
private transient ArrayList<T> systemList;
private transient ArrayList<T> userList;
public ListenerList() {
super();
}
/**
* Adds system listener to this list.
*
* @param listener - listener to be added.
*/
public void addSystemListener(T listener) {
if (systemList == null) {
systemList = new ArrayList<T>();
}
systemList.add(listener);
}
/**
* Adds user (public) listener to this list.
*
* @param listener - listener to be added.
*/
public void addUserListener(T listener) {
if (listener == null) {
return;
}
// transactionally replace old list
synchronized (this) {
if (userList == null) {
userList = new ArrayList<T>();
userList.add(listener);
return;
}
ArrayList<T> newList = new ArrayList<T>(userList);
newList.add(listener);
userList = newList;
}
}
/**
* Removes user (public) listener to this list.
*
* @param listener - listener to be removed.
*/
public void removeUserListener(Object listener) {
if (listener == null) {
return;
}
// transactionally replace old list
synchronized (this) {
if (userList == null || !userList.contains(listener)) {
return;
}
ArrayList<T> newList = new ArrayList<T>(userList);
newList.remove(listener);
userList = (newList.size() > 0 ? newList : null);
}
}
/**
* Gets all user (public) listeners in one array.
*
* @param emptyArray - empty array, it's for deriving particular listeners class.
* @return array of all user listeners.
*/
public <AT> AT[] getUserListeners(AT[] emptyArray){
synchronized (this) {
return (userList != null ? userList.toArray(emptyArray) : emptyArray);
}
}
/**
* Gets all user (public) listeners in one list.
*
* @return list of all user listeners.
*/
public List<T> getUserListeners() {
synchronized (this) {
if (userList == null || userList.isEmpty()) {
return Collections.emptyList();
}
return new ArrayList<T>(userList);
}
}
public List<T> getSystemListeners() {
synchronized (this) {
if (systemList == null || systemList.isEmpty()) {
return Collections.emptyList();
}
return new ArrayList<T>(systemList);
}
}
/**
* Gets iterator for user listeners.
*
* @return iterator for user listeners.
*/
public Iterator<T> getUserIterator() {
synchronized (this) {
if (userList == null) {
List<T> emptyList = Collections.emptyList();
return emptyList.iterator();
}
return new ReadOnlyIterator<T>(userList.iterator());
}
}
/**
* Gets iterator for system listeners.
*
* @return iterator for system listeners.
*/
public Iterator<T> getSystemIterator() {
return systemList.iterator();
}
private static ArrayList<?> getOnlySerializable(ArrayList<?> list) {
if (list == null) {
return null;
}
ArrayList<Object> result = new ArrayList<Object>();
for (Iterator<?> it = list.iterator(); it.hasNext();) {
Object obj = it.next();
if (obj instanceof Serializable) {
result.add(obj);
}
}
return (result.size() != 0) ? result : null;
}
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeObject(getOnlySerializable(systemList));
stream.writeObject(getOnlySerializable(userList));
}
@SuppressWarnings("unchecked")
private void readObject(ObjectInputStream stream)
throws IOException, ClassNotFoundException {
stream.defaultReadObject();
systemList = (ArrayList<T>)stream.readObject();
userList = (ArrayList<T>)stream.readObject();
}
}
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