    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.multimap;
    018
    019import java.io.IOException;
    020import java.io.ObjectInputStream;
    021import java.io.ObjectOutputStream;
    022import java.io.Serializable;
    023import java.util.ArrayList;
    024import java.util.Collection;
    025import java.util.HashMap;
    026import java.util.Map;
    027
    028import org.apache.commons.collections4.MultiValuedMap;
    029
    030/**
    031 * Implements a {@code ListValuedMap}, using a {@link HashMap} to provide data
    032 * storage and {@link ArrayList}s as value collections. This is the standard
    033 * implementation of a ListValuedMap.
    034 * <p>
    035 * <strong>Note that ArrayListValuedHashMap is not synchronized and is not
    036 * thread-safe.</strong> If you wish to use this map from multiple threads
    037 * concurrently, you must use appropriate synchronization. This class may throw
    038 * exceptions when accessed by concurrent threads without synchronization.
    039 * </p>
    040 *
    041 * @param <K> the type of the keys in this map
    042 * @param <V> the type of the values in this map
    043 * @since 4.1
    044 */
    045public class ArrayListValuedHashMap<K, V> extends AbstractListValuedMap<K, V>
    046    implements Serializable {
    047
    048    /** Serialization Version */
    049    private static final long serialVersionUID = 20151118L;
    050
    051    /**
    052     * The initial map capacity used when none specified in constructor.
    053     */
    054    private static final int DEFAULT_INITIAL_MAP_CAPACITY = 16;
    055
    056    /**
    057     * The initial list capacity when using none specified in constructor.
    058     */
    059    private static final int DEFAULT_INITIAL_LIST_CAPACITY = 3;
    060
    061    /**
    062     * The initial list capacity when creating a new value collection.
    063     */
    064    private final int initialListCapacity;
    065
    066    /**
    067     * Creates an empty ArrayListValuedHashMap with the default initial
    068     * map capacity (16) and the default initial list capacity (3).
    069     */
    070    public ArrayListValuedHashMap() {
    071        this(DEFAULT_INITIAL_MAP_CAPACITY, DEFAULT_INITIAL_LIST_CAPACITY);
    072    }
    073
    074    /**
    075     * Creates an empty ArrayListValuedHashMap with the default initial
    076     * map capacity (16) and the specified initial list capacity.
    077     *
    078     * @param initialListCapacity  the initial capacity used for value collections
    079     */
    080    public ArrayListValuedHashMap(final int initialListCapacity) {
    081        this(DEFAULT_INITIAL_MAP_CAPACITY, initialListCapacity);
    082    }
    083
    084    /**
    085     * Creates an empty ArrayListValuedHashMap with the specified initial
    086     * map and list capacities.
    087     *
    088     * @param initialMapCapacity  the initial hashmap capacity
    089     * @param initialListCapacity  the initial capacity used for value collections
    090     */
    091    public ArrayListValuedHashMap(final int initialMapCapacity, final int initialListCapacity) {
    092        super(new HashMap<>(initialMapCapacity));
    093        this.initialListCapacity = initialListCapacity;
    094    }
    095
    096    /**
    097     * Creates an ArrayListValuedHashMap copying all the mappings of the given map.
    098     *
    099     * @param map a {@code Map} to copy into this map
    100     */
    101    public ArrayListValuedHashMap(final Map<? extends K, ? extends V> map) {
    102        this(map.size(), DEFAULT_INITIAL_LIST_CAPACITY);
    103        super.putAll(map);
    104    }
    105
    106    /**
    107     * Creates an ArrayListValuedHashMap copying all the mappings of the given map.
    108     *
    109     * @param map a {@code MultiValuedMap} to copy into this map
    110     */
    111    public ArrayListValuedHashMap(final MultiValuedMap<? extends K, ? extends V> map) {
    112        this(map.size(), DEFAULT_INITIAL_LIST_CAPACITY);
    113        super.putAll(map);
    114    }
    115
    116    @Override
    117    protected ArrayList<V> createCollection() {
    118        return new ArrayList<>(initialListCapacity);
    119    }
    120
    121    /**
    122     * Deserializes an instance from an ObjectInputStream.
    123     *
    124     * @param in The source ObjectInputStream.
    125     * @throws IOException            Any of the usual Input/Output related exceptions.
    126     * @throws ClassNotFoundException A class of a serialized object cannot be found.
    127     */
    128    private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException {
    129        in.defaultReadObject();
    130        setMap(new HashMap<>());
    131        doReadObject(in);
    132    }
    133
    134    /**
    135     * Trims the capacity of all value collections to their current size.
    136     */
    137    public void trimToSize() {
    138        for (final Collection<V> coll : getMap().values()) {
    139            final ArrayList<V> list = (ArrayList<V>) coll;
    140            list.trimToSize();
    141        }
    142    }
    143
    144    /**
    145     * Serializes this object to an ObjectOutputStream.
    146     *
    147     * @param out the target ObjectOutputStream.
    148     * @throws IOException thrown when an I/O errors occur writing to the target stream.
    149     */
    150    private void writeObject(final ObjectOutputStream out) throws IOException {
    151        out.defaultWriteObject();
    152        doWriteObject(out);
    153    }
    154
    155}