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 *
040 * @param <K> the type of the keys in this map
041 * @param <V> the type of the values in this map
042 * @since 4.1
043 */
044public class ArrayListValuedHashMap<K, V> extends AbstractListValuedMap<K, V>
045    implements Serializable {
046
047    /** Serialization Version */
048    private static final long serialVersionUID = 20151118L;
049
050    /**
051     * The initial map capacity used when none specified in constructor.
052     */
053    private static final int DEFAULT_INITIAL_MAP_CAPACITY = 16;
054
055    /**
056     * The initial list capacity when using none specified in constructor.
057     */
058    private static final int DEFAULT_INITIAL_LIST_CAPACITY = 3;
059
060    /**
061     * The initial list capacity when creating a new value collection.
062     */
063    private final int initialListCapacity;
064
065    /**
066     * Creates an empty ArrayListValuedHashMap with the default initial
067     * map capacity (16) and the default initial list capacity (3).
068     */
069    public ArrayListValuedHashMap() {
070        this(DEFAULT_INITIAL_MAP_CAPACITY, DEFAULT_INITIAL_LIST_CAPACITY);
071    }
072
073    /**
074     * Creates an empty ArrayListValuedHashMap with the default initial
075     * map capacity (16) and the specified initial list capacity.
076     *
077     * @param initialListCapacity  the initial capacity used for value collections
078     */
079    public ArrayListValuedHashMap(final int initialListCapacity) {
080        this(DEFAULT_INITIAL_MAP_CAPACITY, initialListCapacity);
081    }
082
083    /**
084     * Creates an empty ArrayListValuedHashMap with the specified initial
085     * map and list capacities.
086     *
087     * @param initialMapCapacity  the initial hashmap capacity
088     * @param initialListCapacity  the initial capacity used for value collections
089     */
090    public ArrayListValuedHashMap(final int initialMapCapacity, final int initialListCapacity) {
091        super(new HashMap<K, ArrayList<V>>(initialMapCapacity));
092        this.initialListCapacity = initialListCapacity;
093    }
094
095    /**
096     * Creates an ArrayListValuedHashMap copying all the mappings of the given map.
097     *
098     * @param map a <code>MultiValuedMap</code> to copy into this map
099     */
100    public ArrayListValuedHashMap(final MultiValuedMap<? extends K, ? extends V> map) {
101        this(map.size(), DEFAULT_INITIAL_LIST_CAPACITY);
102        super.putAll(map);
103    }
104
105    /**
106     * Creates an ArrayListValuedHashMap copying all the mappings of the given map.
107     *
108     * @param map a <code>Map</code> to copy into this map
109     */
110    public ArrayListValuedHashMap(final Map<? extends K, ? extends V> map) {
111        this(map.size(), DEFAULT_INITIAL_LIST_CAPACITY);
112        super.putAll(map);
113    }
114
115    // -----------------------------------------------------------------------
116    @Override
117    protected ArrayList<V> createCollection() {
118        return new ArrayList<>(initialListCapacity);
119    }
120
121    // -----------------------------------------------------------------------
122    /**
123     * Trims the capacity of all value collections to their current size.
124     */
125    public void trimToSize() {
126        for (final Collection<V> coll : getMap().values()) {
127            final ArrayList<V> list = (ArrayList<V>) coll;
128            list.trimToSize();
129        }
130    }
131
132    // -----------------------------------------------------------------------
133    private void writeObject(final ObjectOutputStream oos) throws IOException {
134        oos.defaultWriteObject();
135        doWriteObject(oos);
136    }
137
138    private void readObject(final ObjectInputStream ois) throws IOException, ClassNotFoundException {
139        ois.defaultReadObject();
140        setMap(new HashMap<K, ArrayList<V>>());
141        doReadObject(ois);
142    }
143
144}