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The Apache Commons Collections package contains types that extend and augment the Java Collections Framework.
/*
* 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.commons.collections4.collection;
import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
import java.util.function.Predicate;
/**
* Decorates another {@link Collection} to synchronize its behaviour
* for a multi-threaded environment.
*
* Iterators must be manually synchronized:
*
*
* synchronized (coll) {
* Iterator it = coll.iterator();
* // do stuff with iterator
* }
*
*
* This class is Serializable from Commons Collections 3.1.
*
*
* @param the type of the elements in the collection
* @since 3.0
*/
public class SynchronizedCollection implements Collection, Serializable {
/** Serialization version */
private static final long serialVersionUID = 2412805092710877986L;
/** The collection to decorate */
private final Collection collection;
/** The object to lock on, needed for List/SortedSet views */
protected final Object lock;
/**
* Factory method to create a synchronized collection.
*
* @param the type of the elements in the collection
* @param coll the collection to decorate, must not be null
* @return a new synchronized collection
* @throws NullPointerException if collection is null
* @since 4.0
*/
public static SynchronizedCollection synchronizedCollection(final Collection coll) {
return new SynchronizedCollection<>(coll);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* @param collection the collection to decorate, must not be null
* @throws NullPointerException if the collection is null
*/
protected SynchronizedCollection(final Collection collection) {
if (collection == null) {
throw new NullPointerException("Collection must not be null.");
}
this.collection = collection;
this.lock = this;
}
/**
* Constructor that wraps (not copies).
*
* @param collection the collection to decorate, must not be null
* @param lock the lock object to use, must not be null
* @throws NullPointerException if the collection or lock is null
*/
protected SynchronizedCollection(final Collection collection, final Object lock) {
if (collection == null) {
throw new NullPointerException("Collection must not be null.");
}
if (lock == null) {
throw new NullPointerException("Lock must not be null.");
}
this.collection = collection;
this.lock = lock;
}
/**
* Gets the collection being decorated.
*
* @return the decorated collection
*/
protected Collection decorated() {
return collection;
}
//-----------------------------------------------------------------------
@Override
public boolean add(final E object) {
synchronized (lock) {
return decorated().add(object);
}
}
@Override
public boolean addAll(final Collection coll) {
synchronized (lock) {
return decorated().addAll(coll);
}
}
@Override
public void clear() {
synchronized (lock) {
decorated().clear();
}
}
@Override
public boolean contains(final Object object) {
synchronized (lock) {
return decorated().contains(object);
}
}
@Override
public boolean containsAll(final Collection coll) {
synchronized (lock) {
return decorated().containsAll(coll);
}
}
@Override
public boolean isEmpty() {
synchronized (lock) {
return decorated().isEmpty();
}
}
/**
* Iterators must be manually synchronized.
*
* synchronized (coll) {
* Iterator it = coll.iterator();
* // do stuff with iterator
* }
*
*
* @return an iterator that must be manually synchronized on the collection
*/
@Override
public Iterator iterator() {
return decorated().iterator();
}
@Override
public Object[] toArray() {
synchronized (lock) {
return decorated().toArray();
}
}
@Override
public T[] toArray(final T[] object) {
synchronized (lock) {
return decorated().toArray(object);
}
}
@Override
public boolean remove(final Object object) {
synchronized (lock) {
return decorated().remove(object);
}
}
/**
* @since 4.4
*/
@Override
public boolean removeIf(final Predicate filter) {
synchronized (lock) {
return decorated().removeIf(filter);
}
}
@Override
public boolean removeAll(final Collection coll) {
synchronized (lock) {
return decorated().removeAll(coll);
}
}
@Override
public boolean retainAll(final Collection coll) {
synchronized (lock) {
return decorated().retainAll(coll);
}
}
@Override
public int size() {
synchronized (lock) {
return decorated().size();
}
}
@Override
public boolean equals(final Object object) {
synchronized (lock) {
if (object == this) {
return true;
}
return object == this || decorated().equals(object);
}
}
@Override
public int hashCode() {
synchronized (lock) {
return decorated().hashCode();
}
}
@Override
public String toString() {
synchronized (lock) {
return decorated().toString();
}
}
}