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 behavior
026 * for a multithreaded 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    /**
038     * Synchronized Set for the MultiSet class.
039     */
040    static class SynchronizedSet<T> extends SynchronizedCollection<T> implements Set<T> {
041        /** Serialization version */
042        private static final long serialVersionUID = 20150629L;
043
044        /**
045         * Constructs a new instance.
046         * @param set  the set to decorate
047         * @param lock  the lock to use, shared with the multiset
048         */
049        SynchronizedSet(final Set<T> set, final Object lock) {
050            super(set, lock);
051        }
052    }
053
054    /** Serialization version */
055    private static final long serialVersionUID = 20150629L;
056
057    /**
058     * Factory method to create a synchronized multiset.
059     *
060     * @param <E> the type of the elements in the multiset
061     * @param multiset  the multiset to decorate, must not be null
062     * @return a new synchronized MultiSet
063     * @throws NullPointerException if multiset is null
064     */
065    public static <E> SynchronizedMultiSet<E> synchronizedMultiSet(final MultiSet<E> multiset) {
066        return new SynchronizedMultiSet<>(multiset);
067    }
068
069    /**
070     * Constructor that wraps (not copies).
071     *
072     * @param multiset  the multiset to decorate, must not be null
073     * @throws NullPointerException if multiset is null
074     */
075    protected SynchronizedMultiSet(final MultiSet<E> multiset) {
076        super(multiset);
077    }
078
079    /**
080     * Constructor that wraps (not copies).
081     *
082     * @param multiset  the multiset to decorate, must not be null
083     * @param lock  the lock to use, must not be null
084     * @throws NullPointerException if multiset or lock is null
085     */
086    protected SynchronizedMultiSet(final MultiSet<E> multiset, final Object lock) {
087        super(multiset, lock);
088    }
089
090    @Override
091    public int add(final E object, final int count) {
092        synchronized (lock) {
093            return decorated().add(object, count);
094        }
095    }
096
097    /**
098     * Gets the multiset being decorated.
099     *
100     * @return the decorated multiset
101     */
102    @Override
103    protected MultiSet<E> decorated() {
104        return (MultiSet<E>) super.decorated();
105    }
106
107    @Override
108    public Set<Entry<E>> entrySet() {
109        synchronized (lock) {
110            final Set<MultiSet.Entry<E>> set = decorated().entrySet();
111            return new SynchronizedSet<>(set, lock);
112        }
113    }
114
115    @Override
116    public boolean equals(final Object object) {
117        if (object == this) {
118            return true;
119        }
120        synchronized (lock) {
121            return decorated().equals(object);
122        }
123    }
124
125    @Override
126    public int getCount(final Object object) {
127        synchronized (lock) {
128            return decorated().getCount(object);
129        }
130    }
131
132    @Override
133    public int hashCode() {
134        synchronized (lock) {
135            return decorated().hashCode();
136        }
137    }
138
139    @Override
140    public int remove(final Object object, final int count) {
141        synchronized (lock) {
142            return decorated().remove(object, count);
143        }
144    }
145
146    @Override
147    public int setCount(final E object, final int count) {
148        synchronized (lock) {
149            return decorated().setCount(object, count);
150        }
151    }
152
153    @Override
154    public Set<E> uniqueSet() {
155        synchronized (lock) {
156            final Set<E> set = decorated().uniqueSet();
157            return new SynchronizedSet<>(set, lock);
158        }
159    }
160
161}