/*

 * Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package org.apache.commons.collections4.bag;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.io.Serializable;

import java.util.Collection;

import java.util.HashMap;

/**

 * Implements {@code Bag}, using a {@link HashMap} to provide the

 * data storage. This is the standard implementation of a bag.

 * <p>

 * A {@code Bag} stores each object in the collection together with a

 * count of occurrences. Extra methods on the interface allow multiple copies

 * of an object to be added or removed at once. It is important to read the

 * interface javadoc carefully as several methods violate the

 * {@link Collection} interface specification.

 * </p>

 *

 * @param <E> the type of elements in this bag

 * @since 3.0 (previously in main package v2.0)

 */

public class HashBag<E> extends AbstractMapBag<E> implements Serializable {

    /** Serial version lock */

    private static final long serialVersionUID = -6561115435802554013L;

    /**

     * Constructs an empty {@link HashBag}.

     */

    public HashBag() {

        super(new HashMap<E, MutableInteger>());

    }

    /**

     * Constructs a bag containing all the members of the given collection.

     *

     * @param coll  a collection to copy into this bag

     */

    public HashBag(final Collection<? extends E> coll) {

        this();

        addAll(coll);

    }

    //-----------------------------------------------------------------------

    /**

     * Write the bag out using a custom routine.

     *

     * @param out  the output stream

     * @throws IOException if an error occurs while writing to the stream

     */

    private void writeObject(final ObjectOutputStream out) throws IOException {

        out.defaultWriteObject();

        super.doWriteObject(out);

    }

    /**

     * Read the bag in using a custom routine.

     *

     * @param in  the input stream

     * @throws IOException if an error occurs while reading from the stream

     * @throws ClassNotFoundException if an object read from the stream can not be loaded

     */

    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {

        in.defaultReadObject();

        super.doReadObject(new HashMap<E, MutableInteger>(), in);

    }

}