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 * </p>
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 HashSetValuedHashMap<K, V> extends AbstractSetValuedMap<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 set capacity when using none specified in constructor.
057     */
058    private static final int DEFAULT_INITIAL_SET_CAPACITY = 3;
059
060    /**
061     * The initial list capacity when creating a new value collection.
062     */
063    private final int initialSetCapacity;
064
065    /**
066     * Creates an empty HashSetValuedHashMap with the default initial
067     * map capacity (16) and the default initial set capacity (3).
068     */
069    public HashSetValuedHashMap() {
070        this(DEFAULT_INITIAL_MAP_CAPACITY, DEFAULT_INITIAL_SET_CAPACITY);
071    }
072
073    /**
074     * Creates an empty HashSetValuedHashMap with the default initial
075     * map capacity (16) and the specified initial set capacity.
076     *
077     * @param initialSetCapacity  the initial capacity used for value collections
078     */
079    public HashSetValuedHashMap(final int initialSetCapacity) {
080        this(DEFAULT_INITIAL_MAP_CAPACITY, initialSetCapacity);
081    }
082
083    /**
084     * Creates an empty HashSetValuedHashMap with the specified initial
085     * map and list capacities.
086     *
087     * @param initialMapCapacity  the initial hashmap capacity
088     * @param initialSetCapacity  the initial capacity used for value collections
089     */
090    public HashSetValuedHashMap(final int initialMapCapacity, final int initialSetCapacity) {
091        super(new HashMap<K, HashSet<V>>(initialMapCapacity));
092        this.initialSetCapacity = initialSetCapacity;
093    }
094
095    /**
096     * Creates an HashSetValuedHashMap copying all the mappings of the given map.
097     *
098     * @param map a <code>MultiValuedMap</code> to copy into this map
099     */
100    public HashSetValuedHashMap(final MultiValuedMap<? extends K, ? extends V> map) {
101        this(map.size(), DEFAULT_INITIAL_SET_CAPACITY);
102        super.putAll(map);
103    }
104
105    /**
106     * Creates an HashSetValuedHashMap copying all the mappings of the given map.
107     *
108     * @param map a <code>Map</code> to copy into this map
109     */
110    public HashSetValuedHashMap(final Map<? extends K, ? extends V> map) {
111        this(map.size(), DEFAULT_INITIAL_SET_CAPACITY);
112        super.putAll(map);
113    }
114
115    // -----------------------------------------------------------------------
116    @Override
117    protected HashSet<V> createCollection() {
118        return new HashSet<>(initialSetCapacity);
119    }
120
121    // -----------------------------------------------------------------------
122    private void writeObject(final ObjectOutputStream oos) throws IOException {
123        oos.defaultWriteObject();
124        doWriteObject(oos);
125    }
126
127    private void readObject(final ObjectInputStream ois) throws IOException, ClassNotFoundException {
128        ois.defaultReadObject();
129        setMap(new HashMap<K, HashSet<V>>());
130        doReadObject(ois);
131    }
132
133}