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.bag;
018
019import java.util.Set;
020
021import org.apache.commons.collections4.Bag;
022import org.apache.commons.collections4.collection.SynchronizedCollection;
023
024/**
025 * Decorates another {@link Bag} to synchronize its behaviour
026 * for a multi-threaded environment.
027 * <p>
028 * Methods are synchronized, then forwarded to the decorated bag.
029 * Iterators must be separately synchronized around the loop.
030 * <p>
031 * This class is Serializable from Commons Collections 3.1.
032 *
033 * @param <E> the type of elements in this bag
034 * @since 3.0
035 */
036public class SynchronizedBag<E> extends SynchronizedCollection<E> implements Bag<E> {
037
038    /** Serialization version */
039    private static final long serialVersionUID = 8084674570753837109L;
040
041    /**
042     * Factory method to create a synchronized bag.
043     *
044     * @param <E> the type of the elements in the bag
045     * @param bag  the bag to decorate, must not be null
046     * @return a new synchronized Bag
047     * @throws NullPointerException if bag is null
048     * @since 4.0
049     */
050    public static <E> SynchronizedBag<E> synchronizedBag(final Bag<E> bag) {
051        return new SynchronizedBag<>(bag);
052    }
053
054    //-----------------------------------------------------------------------
055    /**
056     * Constructor that wraps (not copies).
057     *
058     * @param bag  the bag to decorate, must not be null
059     * @throws NullPointerException if bag is null
060     */
061    protected SynchronizedBag(final Bag<E> bag) {
062        super(bag);
063    }
064
065    /**
066     * Constructor that wraps (not copies).
067     *
068     * @param bag  the bag to decorate, must not be null
069     * @param lock  the lock to use, must not be null
070     * @throws NullPointerException if bag or lock is null
071     */
072    protected SynchronizedBag(final Bag<E> bag, final Object lock) {
073        super(bag, lock);
074    }
075
076    /**
077     * Gets the bag being decorated.
078     *
079     * @return the decorated bag
080     */
081    protected Bag<E> getBag() {
082        return (Bag<E>) decorated();
083    }
084
085    @Override
086    public boolean equals(final Object object) {
087        if (object == this) {
088            return true;
089        }
090        synchronized (lock) {
091            return getBag().equals(object);
092        }
093    }
094
095    @Override
096    public int hashCode() {
097        synchronized (lock) {
098            return getBag().hashCode();
099        }
100    }
101
102    //-----------------------------------------------------------------------
103
104    @Override
105    public boolean add(final E object, final int count) {
106        synchronized (lock) {
107            return getBag().add(object, count);
108        }
109    }
110
111    @Override
112    public boolean remove(final Object object, final int count) {
113        synchronized (lock) {
114            return getBag().remove(object, count);
115        }
116    }
117
118    @Override
119    public Set<E> uniqueSet() {
120        synchronized (lock) {
121            final Set<E> set = getBag().uniqueSet();
122            return new SynchronizedBagSet(set, lock);
123        }
124    }
125
126    @Override
127    public int getCount(final Object object) {
128        synchronized (lock) {
129            return getBag().getCount(object);
130        }
131    }
132
133    //-----------------------------------------------------------------------
134    /**
135     * Synchronized Set for the Bag class.
136     */
137    class SynchronizedBagSet extends SynchronizedCollection<E> implements Set<E> {
138        /** Serialization version */
139        private static final long serialVersionUID = 2990565892366827855L;
140
141        /**
142         * Constructor.
143         * @param set  the set to decorate
144         * @param lock  the lock to use, shared with the bag
145         */
146        SynchronizedBagSet(final Set<E> set, final Object lock) {
147            super(set, lock);
148        }
149    }
150
151}