    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 *      https://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.io.IOException;
    020import java.io.ObjectInputStream;
    021import java.io.ObjectOutputStream;
    022import java.io.Serializable;
    023import java.util.Collection;
    024import java.util.HashMap;
    025
    026import org.apache.commons.collections4.multiset.HashMultiSet;
    027
    028/**
    029 * Implements {@code Bag}, using a {@link HashMap} to provide the
    030 * data storage. This is the standard implementation of a bag.
    031 * <p>
    032 * A {@code Bag} stores each object in the collection together with a
    033 * count of occurrences. Extra methods on the interface allow multiple copies
    034 * of an object to be added or removed at once. It is important to read the
    035 * interface Javadoc carefully as several methods violate the
    036 * {@link Collection} interface specification.
    037 * </p>
    038 * <p>
    039 * <strong>Note that HashBag is not synchronized and is not thread-safe.</strong>
    040 * If you wish to use this bag from multiple threads concurrently, you must use
    041 * appropriate synchronization. The simplest approach is to wrap this bag using
    042 * {@link org.apache.commons.collections4.BagUtils#synchronizedBag(org.apache.commons.collections4.Bag)
    043 * BagUtils.synchronizedBag(Bag)}.
    044 * Unsynchronized concurrent modification can corrupt the structure of the backing
    045 * {@link HashMap}, which may cause subsequent operations to throw exceptions,
    046 * return incorrect results, or loop indefinitely.
    047 * </p>
    048 *
    049 * @param <E> The type of elements in this bag
    050 * @since 3.0 (previously in main package v2.0)
    051 * @deprecated Since 4.6.0, use {@link HashMultiSet} instead.
    052 */
    053@Deprecated
    054public class HashBag<E> extends AbstractMapBag<E> implements Serializable {
    055
    056    /** Serial version lock */
    057    private static final long serialVersionUID = -6561115435802554013L;
    058
    059    /**
    060     * Constructs an empty {@link HashBag}.
    061     */
    062    public HashBag() {
    063        super(new HashMap<>());
    064    }
    065
    066    /**
    067     * Constructs a bag containing all the members of the given Collection.
    068     *
    069     * @param collection A collection to copy into this bag.
    070     */
    071    public HashBag(final Collection<? extends E> collection) {
    072        this();
    073        addAll(collection);
    074    }
    075
    076    /**
    077     * Constructs a bag containing all the members of the given Iterable.
    078     *
    079     * @param iterable An iterable to copy into this bag.
    080     * @since 4.5.0-M3
    081     */
    082    public HashBag(final Iterable<? extends E> iterable) {
    083        super(new HashMap<>(), iterable);
    084    }
    085
    086    /**
    087     * Deserializes the bag in using a custom routine.
    088     *
    089     * @param in  The input stream
    090     * @throws IOException Thrown if an error occurs while reading from the stream
    091     * @throws ClassNotFoundException if an object read from the stream cannot be loaded
    092     */
    093    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    094        in.defaultReadObject();
    095        super.doReadObject(new HashMap<>(), in);
    096    }
    097
    098    /**
    099     * Serializes this object to an ObjectOutputStream.
    100     *
    101     * @param out The target ObjectOutputStream.
    102     * @throws IOException thrown when an I/O errors occur writing to the target stream.
    103     */
    104    private void writeObject(final ObjectOutputStream out) throws IOException {
    105        out.defaultWriteObject();
    106        super.doWriteObject(out);
    107    }
    108
    109}