    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 */
    017package org.apache.commons.collections4.collection;
    018
    019import java.io.Serializable;
    020import java.util.Collection;
    021import java.util.Iterator;
    022
    023/**
    024 * Decorates another {@link Collection} to synchronize its behaviour
    025 * for a multi-threaded environment.
    026 * <p>
    027 * Iterators must be manually synchronized:
    028 * <pre>
    029 * synchronized (coll) {
    030 *   Iterator it = coll.iterator();
    031 *   // do stuff with iterator
    032 * }
    033 * </pre>
    034 * <p>
    035 * This class is Serializable from Commons Collections 3.1.
    036 *
    037 * @param <E> the type of the elements in the collection
    038 * @since 3.0
    039 */
    040public class SynchronizedCollection<E> implements Collection<E>, Serializable {
    041
    042    /** Serialization version */
    043    private static final long serialVersionUID = 2412805092710877986L;
    044
    045    /** The collection to decorate */
    046    private final Collection<E> collection;
    047    /** The object to lock on, needed for List/SortedSet views */
    048    protected final Object lock;
    049
    050    /**
    051     * Factory method to create a synchronized collection.
    052     *
    053     * @param <T> the type of the elements in the collection
    054     * @param coll  the collection to decorate, must not be null
    055     * @return a new synchronized collection
    056     * @throws NullPointerException if collection is null
    057     * @since 4.0
    058     */
    059    public static <T> SynchronizedCollection<T> synchronizedCollection(final Collection<T> coll) {
    060        return new SynchronizedCollection<>(coll);
    061    }
    062
    063    //-----------------------------------------------------------------------
    064    /**
    065     * Constructor that wraps (not copies).
    066     *
    067     * @param collection  the collection to decorate, must not be null
    068     * @throws NullPointerException if the collection is null
    069     */
    070    protected SynchronizedCollection(final Collection<E> collection) {
    071        if (collection == null) {
    072            throw new NullPointerException("Collection must not be null.");
    073        }
    074        this.collection = collection;
    075        this.lock = this;
    076    }
    077
    078    /**
    079     * Constructor that wraps (not copies).
    080     *
    081     * @param collection  the collection to decorate, must not be null
    082     * @param lock  the lock object to use, must not be null
    083     * @throws NullPointerException if the collection or lock is null
    084     */
    085    protected SynchronizedCollection(final Collection<E> collection, final Object lock) {
    086        if (collection == null) {
    087            throw new NullPointerException("Collection must not be null.");
    088        }
    089        if (lock == null) {
    090            throw new NullPointerException("Lock must not be null.");
    091        }
    092        this.collection = collection;
    093        this.lock = lock;
    094    }
    095
    096    /**
    097     * Gets the collection being decorated.
    098     *
    099     * @return the decorated collection
    100     */
    101    protected Collection<E> decorated() {
    102        return collection;
    103    }
    104
    105    //-----------------------------------------------------------------------
    106
    107    @Override
    108    public boolean add(final E object) {
    109        synchronized (lock) {
    110            return decorated().add(object);
    111        }
    112    }
    113
    114    @Override
    115    public boolean addAll(final Collection<? extends E> coll) {
    116        synchronized (lock) {
    117            return decorated().addAll(coll);
    118        }
    119    }
    120
    121    @Override
    122    public void clear() {
    123        synchronized (lock) {
    124            decorated().clear();
    125        }
    126    }
    127
    128    @Override
    129    public boolean contains(final Object object) {
    130        synchronized (lock) {
    131            return decorated().contains(object);
    132        }
    133    }
    134
    135    @Override
    136    public boolean containsAll(final Collection<?> coll) {
    137        synchronized (lock) {
    138            return decorated().containsAll(coll);
    139        }
    140    }
    141
    142    @Override
    143    public boolean isEmpty() {
    144        synchronized (lock) {
    145            return decorated().isEmpty();
    146        }
    147    }
    148
    149    /**
    150     * Iterators must be manually synchronized.
    151     * <pre>
    152     * synchronized (coll) {
    153     *   Iterator it = coll.iterator();
    154     *   // do stuff with iterator
    155     * }
    156     * </pre>
    157     *
    158     * @return an iterator that must be manually synchronized on the collection
    159     */
    160    @Override
    161    public Iterator<E> iterator() {
    162        return decorated().iterator();
    163    }
    164
    165    @Override
    166    public Object[] toArray() {
    167        synchronized (lock) {
    168            return decorated().toArray();
    169        }
    170    }
    171
    172    @Override
    173    public <T> T[] toArray(final T[] object) {
    174        synchronized (lock) {
    175            return decorated().toArray(object);
    176        }
    177    }
    178
    179    @Override
    180    public boolean remove(final Object object) {
    181        synchronized (lock) {
    182            return decorated().remove(object);
    183        }
    184    }
    185
    186    @Override
    187    public boolean removeAll(final Collection<?> coll) {
    188        synchronized (lock) {
    189            return decorated().removeAll(coll);
    190        }
    191    }
    192
    193    @Override
    194    public boolean retainAll(final Collection<?> coll) {
    195        synchronized (lock) {
    196            return decorated().retainAll(coll);
    197        }
    198    }
    199
    200    @Override
    201    public int size() {
    202        synchronized (lock) {
    203            return decorated().size();
    204        }
    205    }
    206
    207    @Override
    208    public boolean equals(final Object object) {
    209        synchronized (lock) {
    210            if (object == this) {
    211                return true;
    212            }
    213            return object == this || decorated().equals(object);
    214        }
    215    }
    216
    217    @Override
    218    public int hashCode() {
    219        synchronized (lock) {
    220            return decorated().hashCode();
    221        }
    222    }
    223
    224    @Override
    225    public String toString() {
    226        synchronized (lock) {
    227            return decorated().toString();
    228        }
    229    }
    230
    231}