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.HashMap;
024import java.util.HashSet;
025import java.util.Map;
026
027import org.apache.commons.collections4.MultiValuedMap;
028
029/**
030 * Implements a {@code SetValuedMap}, using a {@link HashMap} to provide data
031 * storage and {@link HashSet}s as value collections. This is the standard
032 * implementation of a SetValuedMap.
033 * <p>
034 * <strong>Note that HashSetValuedHashMap is not synchronized and is not
035 * thread-safe.</strong> If you wish to use this map from multiple threads
036 * concurrently, you must use appropriate synchronization. This class may throw
037 * exceptions when accessed by concurrent threads without synchronization.
038 *
039 * @param <K> the type of the keys in this map
040 * @param <V> the type of the values in this map
041 * @since 4.1
042 */
043public class HashSetValuedHashMap<K, V> extends AbstractSetValuedMap<K, V>
044    implements Serializable {
045
046    /** Serialization Version */
047    private static final long serialVersionUID = 20151118L;
048
049    /**
050     * The initial map capacity used when none specified in constructor.
051     */
052    private static final int DEFAULT_INITIAL_MAP_CAPACITY = 16;
053
054    /**
055     * The initial set capacity when using none specified in constructor.
056     */
057    private static final int DEFAULT_INITIAL_SET_CAPACITY = 3;
058
059    /**
060     * The initial list capacity when creating a new value collection.
061     */
062    private final int initialSetCapacity;
063
064    /**
065     * Creates an empty HashSetValuedHashMap with the default initial
066     * map capacity (16) and the default initial set capacity (3).
067     */
068    public HashSetValuedHashMap() {
069        this(DEFAULT_INITIAL_MAP_CAPACITY, DEFAULT_INITIAL_SET_CAPACITY);
070    }
071
072    /**
073     * Creates an empty HashSetValuedHashMap with the default initial
074     * map capacity (16) and the specified initial set capacity.
075     *
076     * @param initialSetCapacity  the initial capacity used for value collections
077     */
078    public HashSetValuedHashMap(final int initialSetCapacity) {
079        this(DEFAULT_INITIAL_MAP_CAPACITY, initialSetCapacity);
080    }
081
082    /**
083     * Creates an empty HashSetValuedHashMap with the specified initial
084     * map and list capacities.
085     *
086     * @param initialMapCapacity  the initial hashmap capacity
087     * @param initialSetCapacity  the initial capacity used for value collections
088     */
089    public HashSetValuedHashMap(final int initialMapCapacity, final int initialSetCapacity) {
090        super(new HashMap<K, HashSet<V>>(initialMapCapacity));
091        this.initialSetCapacity = initialSetCapacity;
092    }
093
094    /**
095     * Creates an HashSetValuedHashMap copying all the mappings of the given map.
096     *
097     * @param map a <code>MultiValuedMap</code> to copy into this map
098     */
099    public HashSetValuedHashMap(final MultiValuedMap<? extends K, ? extends V> map) {
100        this(map.size(), DEFAULT_INITIAL_SET_CAPACITY);
101        super.putAll(map);
102    }
103
104    /**
105     * Creates an HashSetValuedHashMap copying all the mappings of the given map.
106     *
107     * @param map a <code>Map</code> to copy into this map
108     */
109    public HashSetValuedHashMap(final Map<? extends K, ? extends V> map) {
110        this(map.size(), DEFAULT_INITIAL_SET_CAPACITY);
111        super.putAll(map);
112    }
113
114    // -----------------------------------------------------------------------
115    @Override
116    protected HashSet<V> createCollection() {
117        return new HashSet<>(initialSetCapacity);
118    }
119
120    // -----------------------------------------------------------------------
121    private void writeObject(final ObjectOutputStream oos) throws IOException {
122        oos.defaultWriteObject();
123        doWriteObject(oos);
124    }
125
126    private void readObject(final ObjectInputStream ois) throws IOException, ClassNotFoundException {
127        ois.defaultReadObject();
128        setMap(new HashMap<K, HashSet<V>>());
129        doReadObject(ois);
130    }
131
132}