    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.io.IOException;
    020import java.io.ObjectInputStream;
    021import java.io.ObjectOutputStream;
    022import java.io.Serializable;
    023import java.util.Collection;
    024import java.util.HashMap;
    025
    026/**
    027 * Implements {@code Bag}, using a {@link HashMap} to provide the
    028 * data storage. This is the standard implementation of a bag.
    029 * <p>
    030 * A {@code Bag} stores each object in the collection together with a
    031 * count of occurrences. Extra methods on the interface allow multiple copies
    032 * of an object to be added or removed at once. It is important to read the
    033 * interface javadoc carefully as several methods violate the
    034 * {@link Collection} interface specification.
    035 *
    036 * @param <E> the type of elements in this bag
    037 * @since 3.0 (previously in main package v2.0)
    038 */
    039public class HashBag<E> extends AbstractMapBag<E> implements Serializable {
    040
    041    /** Serial version lock */
    042    private static final long serialVersionUID = -6561115435802554013L;
    043
    044    /**
    045     * Constructs an empty {@link HashBag}.
    046     */
    047    public HashBag() {
    048        super(new HashMap<E, MutableInteger>());
    049    }
    050
    051    /**
    052     * Constructs a bag containing all the members of the given collection.
    053     *
    054     * @param coll  a collection to copy into this bag
    055     */
    056    public HashBag(final Collection<? extends E> coll) {
    057        this();
    058        addAll(coll);
    059    }
    060
    061    //-----------------------------------------------------------------------
    062    /**
    063     * Write the bag out using a custom routine.
    064     *
    065     * @param out  the output stream
    066     * @throws IOException if an error occurs while writing to the stream
    067     */
    068    private void writeObject(final ObjectOutputStream out) throws IOException {
    069        out.defaultWriteObject();
    070        super.doWriteObject(out);
    071    }
    072
    073    /**
    074     * Read the bag in using a custom routine.
    075     *
    076     * @param in  the input stream
    077     * @throws IOException if an error occurs while reading from the stream
    078     * @throws ClassNotFoundException if an object read from the stream can not be loaded
    079     */
    080    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    081        in.defaultReadObject();
    082        super.doReadObject(new HashMap<E, MutableInteger>(), in);
    083    }
    084
    085}