Back to index...

	/*
	* 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.
	* <p>
	* Iterators must be manually synchronized:
	* </p>
	* <pre>
	* synchronized (coll) {
	* Iterator it = coll.iterator();
	* // do stuff with iterator
	* }
	* </pre>
	* <p>
	* This class is Serializable from Commons Collections 3.1.
	* </p>
	*
	* @param <E> the type of the elements in the collection
	* @since 3.0
	*/
	public class SynchronizedCollection<E> implements Collection<E>, Serializable {

	/** Serialization version */
	private static final long serialVersionUID = 2412805092710877986L;

	/** The collection to decorate */
	private final Collection<E> collection;
	/** The object to lock on, needed for List/SortedSet views */
	protected final Object lock;

	/**
	* Factory method to create a synchronized collection.
	*
	* @param <T> 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 <T> SynchronizedCollection<T> synchronizedCollection(final Collection<T> 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<E> 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<E> 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<E> decorated() {
	return collection;
	}

	//-----------------------------------------------------------------------

	@Override
	public boolean add(final E object) {
	synchronized (lock) {
	return decorated().add(object);
	}
	}

	@Override
	public boolean addAll(final Collection<? extends E> 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.
	* <pre>
	* synchronized (coll) {
	* Iterator it = coll.iterator();
	* // do stuff with iterator
	* }
	* </pre>
	*
	* @return an iterator that must be manually synchronized on the collection
	*/
	@Override
	public Iterator<E> iterator() {
	return decorated().iterator();
	}

	@Override
	public Object[] toArray() {
	synchronized (lock) {
	return decorated().toArray();
	}
	}

	@Override
	public <T> 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<? super E> 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();
	}
	}

	}

Back to index...