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.multiset;
018
019import java.util.Set;
020
021import org.apache.commons.collections4.MultiSet;
022import org.apache.commons.collections4.collection.SynchronizedCollection;
023
024/**
025 * Decorates another {@link MultiSet} to synchronize its behaviour
026 * for a multi-threaded environment.
027 * <p>
028 * Methods are synchronized, then forwarded to the decorated multiset.
029 * Iterators must be separately synchronized around the loop.
030 * </p>
031 *
032 * @param <E> the type held in the multiset
033 * @since 4.1
034 */
035public class SynchronizedMultiSet<E> extends SynchronizedCollection<E> implements MultiSet<E> {
036
037    /** Serialization version */
038    private static final long serialVersionUID = 20150629L;
039
040    /**
041     * Factory method to create a synchronized multiset.
042     *
043     * @param <E> the type of the elements in the multiset
044     * @param multiset  the multiset to decorate, must not be null
045     * @return a new synchronized MultiSet
046     * @throws NullPointerException if multiset is null
047     */
048    public static <E> SynchronizedMultiSet<E> synchronizedMultiSet(final MultiSet<E> multiset) {
049        return new SynchronizedMultiSet<>(multiset);
050    }
051
052    //-----------------------------------------------------------------------
053    /**
054     * Constructor that wraps (not copies).
055     *
056     * @param multiset  the multiset to decorate, must not be null
057     * @throws NullPointerException if multiset is null
058     */
059    protected SynchronizedMultiSet(final MultiSet<E> multiset) {
060        super(multiset);
061    }
062
063    /**
064     * Constructor that wraps (not copies).
065     *
066     * @param multiset  the multiset to decorate, must not be null
067     * @param lock  the lock to use, must not be null
068     * @throws NullPointerException if multiset or lock is null
069     */
070    protected SynchronizedMultiSet(final MultiSet<E> multiset, final Object lock) {
071        super(multiset, lock);
072    }
073
074    /**
075     * Gets the multiset being decorated.
076     *
077     * @return the decorated multiset
078     */
079    @Override
080    protected MultiSet<E> decorated() {
081        return (MultiSet<E>) super.decorated();
082    }
083
084    @Override
085    public boolean equals(final Object object) {
086        if (object == this) {
087            return true;
088        }
089        synchronized (lock) {
090            return decorated().equals(object);
091        }
092    }
093
094    @Override
095    public int hashCode() {
096        synchronized (lock) {
097            return decorated().hashCode();
098        }
099    }
100
101    //-----------------------------------------------------------------------
102
103    @Override
104    public int add(final E object, final int count) {
105        synchronized (lock) {
106            return decorated().add(object, count);
107        }
108    }
109
110    @Override
111    public int remove(final Object object, final int count) {
112        synchronized (lock) {
113            return decorated().remove(object, count);
114        }
115    }
116
117    @Override
118    public int getCount(final Object object) {
119        synchronized (lock) {
120            return decorated().getCount(object);
121        }
122    }
123
124    @Override
125    public int setCount(final E object, final int count) {
126        synchronized (lock) {
127            return decorated().setCount(object, count);
128        }
129    }
130
131    @Override
132    public Set<E> uniqueSet() {
133        synchronized (lock) {
134            final Set<E> set = decorated().uniqueSet();
135            return new SynchronizedSet<>(set, lock);
136        }
137    }
138
139    @Override
140    public Set<Entry<E>> entrySet() {
141        synchronized (lock) {
142            final Set<MultiSet.Entry<E>> set = decorated().entrySet();
143            return new SynchronizedSet<>(set, lock);
144        }
145    }
146
147    //-----------------------------------------------------------------------
148    /**
149     * Synchronized Set for the MultiSet class.
150     */
151    static class SynchronizedSet<T> extends SynchronizedCollection<T> implements Set<T> {
152        /** Serialization version */
153        private static final long serialVersionUID = 20150629L;
154
155        /**
156         * Constructor.
157         * @param set  the set to decorate
158         * @param lock  the lock to use, shared with the multiset
159         */
160        SynchronizedSet(final Set<T> set, final Object lock) {
161            super(set, lock);
162        }
163    }
164
165}