/*
 * 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.multimap;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Map;

import org.apache.commons.collections4.MultiValuedMap;

Implements a ListValuedMap, using a HashMap to provide data storage and ArrayLists as value collections. This is the standard implementation of a ListValuedMap.

Note that ArrayListValuedHashMap is not synchronized and is not thread-safe. If you wish to use this map from multiple threads concurrently, you must use appropriate synchronization. This class may throw exceptions when accessed by concurrent threads without synchronization.

Type parameters:
  • <K> – the type of the keys in this map
  • <V> – the type of the values in this map
Since:4.1
/** * Implements a {@code ListValuedMap}, using a {@link HashMap} to provide data * storage and {@link ArrayList}s as value collections. This is the standard * implementation of a ListValuedMap. * <p> * <strong>Note that ArrayListValuedHashMap is not synchronized and is not * thread-safe.</strong> If you wish to use this map from multiple threads * concurrently, you must use appropriate synchronization. This class may throw * exceptions when accessed by concurrent threads without synchronization. * * @param <K> the type of the keys in this map * @param <V> the type of the values in this map * @since 4.1 */
public class ArrayListValuedHashMap<K, V> extends AbstractListValuedMap<K, V> implements Serializable {
Serialization Version
/** Serialization Version */
private static final long serialVersionUID = 20151118L;
The initial map capacity used when none specified in constructor.
/** * The initial map capacity used when none specified in constructor. */
private static final int DEFAULT_INITIAL_MAP_CAPACITY = 16;
The initial list capacity when using none specified in constructor.
/** * The initial list capacity when using none specified in constructor. */
private static final int DEFAULT_INITIAL_LIST_CAPACITY = 3;
The initial list capacity when creating a new value collection.
/** * The initial list capacity when creating a new value collection. */
private final int initialListCapacity;
Creates an empty ArrayListValuedHashMap with the default initial map capacity (16) and the default initial list capacity (3).
/** * Creates an empty ArrayListValuedHashMap with the default initial * map capacity (16) and the default initial list capacity (3). */
public ArrayListValuedHashMap() { this(DEFAULT_INITIAL_MAP_CAPACITY, DEFAULT_INITIAL_LIST_CAPACITY); }
Creates an empty ArrayListValuedHashMap with the default initial map capacity (16) and the specified initial list capacity.
Params:
  • initialListCapacity – the initial capacity used for value collections
/** * Creates an empty ArrayListValuedHashMap with the default initial * map capacity (16) and the specified initial list capacity. * * @param initialListCapacity the initial capacity used for value collections */
public ArrayListValuedHashMap(final int initialListCapacity) { this(DEFAULT_INITIAL_MAP_CAPACITY, initialListCapacity); }
Creates an empty ArrayListValuedHashMap with the specified initial map and list capacities.
Params:
  • initialMapCapacity – the initial hashmap capacity
  • initialListCapacity – the initial capacity used for value collections
/** * Creates an empty ArrayListValuedHashMap with the specified initial * map and list capacities. * * @param initialMapCapacity the initial hashmap capacity * @param initialListCapacity the initial capacity used for value collections */
public ArrayListValuedHashMap(final int initialMapCapacity, final int initialListCapacity) { super(new HashMap<K, ArrayList<V>>(initialMapCapacity)); this.initialListCapacity = initialListCapacity; }
Creates an ArrayListValuedHashMap copying all the mappings of the given map.
Params:
  • map – a MultiValuedMap to copy into this map
/** * Creates an ArrayListValuedHashMap copying all the mappings of the given map. * * @param map a <code>MultiValuedMap</code> to copy into this map */
public ArrayListValuedHashMap(final MultiValuedMap<? extends K, ? extends V> map) { this(map.size(), DEFAULT_INITIAL_LIST_CAPACITY); super.putAll(map); }
Creates an ArrayListValuedHashMap copying all the mappings of the given map.
Params:
  • map – a Map to copy into this map
/** * Creates an ArrayListValuedHashMap copying all the mappings of the given map. * * @param map a <code>Map</code> to copy into this map */
public ArrayListValuedHashMap(final Map<? extends K, ? extends V> map) { this(map.size(), DEFAULT_INITIAL_LIST_CAPACITY); super.putAll(map); } // ----------------------------------------------------------------------- @Override protected ArrayList<V> createCollection() { return new ArrayList<>(initialListCapacity); } // -----------------------------------------------------------------------
Trims the capacity of all value collections to their current size.
/** * Trims the capacity of all value collections to their current size. */
public void trimToSize() { for (final Collection<V> coll : getMap().values()) { final ArrayList<V> list = (ArrayList<V>) coll; list.trimToSize(); } } // ----------------------------------------------------------------------- private void writeObject(final ObjectOutputStream oos) throws IOException { oos.defaultWriteObject(); doWriteObject(oos); } private void readObject(final ObjectInputStream ois) throws IOException, ClassNotFoundException { ois.defaultReadObject(); setMap(new HashMap<K, ArrayList<V>>()); doReadObject(ois); } }