| /* |
| * Copyright (C) 2007 The Guava Authors |
| * |
| * Licensed 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 com.google.common.collect; |
| |
| import static com.google.common.collect.CollectPreconditions.checkNonnegative; |
| |
| import com.google.common.annotations.GwtCompatible; |
| import com.google.common.annotations.VisibleForTesting; |
| |
| import java.util.ArrayList; |
| import java.util.Collection; |
| import java.util.HashMap; |
| import java.util.List; |
| |
| /** |
| * Implementation of {@code Multimap} that uses an {@code ArrayList} to store |
| * the values for a given key. A {@link HashMap} associates each key with an |
| * {@link ArrayList} of values. |
| * |
| * <p>When iterating through the collections supplied by this class, the |
| * ordering of values for a given key agrees with the order in which the values |
| * were added. |
| * |
| * <p>This multimap allows duplicate key-value pairs. After adding a new |
| * key-value pair equal to an existing key-value pair, the {@code |
| * ArrayListMultimap} will contain entries for both the new value and the old |
| * value. |
| * |
| * <p>Keys and values may be null. All optional multimap methods are supported, |
| * and all returned views are modifiable. |
| * |
| * <p>The lists returned by {@link #get}, {@link #removeAll}, and {@link |
| * #replaceValues} all implement {@link java.util.RandomAccess}. |
| * |
| * <p>This class is not threadsafe when any concurrent operations update the |
| * multimap. Concurrent read operations will work correctly. To allow concurrent |
| * update operations, wrap your multimap with a call to {@link |
| * Multimaps#synchronizedListMultimap}. |
| * |
| * <p>See the Guava User Guide article on <a href= |
| * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multimap"> |
| * {@code Multimap}</a>. |
| * |
| * @author Jared Levy |
| * @since 2.0 (imported from Google Collections Library) |
| */ |
| @GwtCompatible(serializable = true, emulated = true) |
| public final class ArrayListMultimap<K, V> extends AbstractListMultimap<K, V> { |
| // Default from ArrayList |
| private static final int DEFAULT_VALUES_PER_KEY = 3; |
| |
| @VisibleForTesting transient int expectedValuesPerKey; |
| |
| /** |
| * Creates a new, empty {@code ArrayListMultimap} with the default initial |
| * capacities. |
| */ |
| public static <K, V> ArrayListMultimap<K, V> create() { |
| return new ArrayListMultimap<K, V>(); |
| } |
| |
| /** |
| * Constructs an empty {@code ArrayListMultimap} with enough capacity to hold |
| * the specified numbers of keys and values without resizing. |
| * |
| * @param expectedKeys the expected number of distinct keys |
| * @param expectedValuesPerKey the expected average number of values per key |
| * @throws IllegalArgumentException if {@code expectedKeys} or {@code |
| * expectedValuesPerKey} is negative |
| */ |
| public static <K, V> ArrayListMultimap<K, V> create( |
| int expectedKeys, int expectedValuesPerKey) { |
| return new ArrayListMultimap<K, V>(expectedKeys, expectedValuesPerKey); |
| } |
| |
| /** |
| * Constructs an {@code ArrayListMultimap} with the same mappings as the |
| * specified multimap. |
| * |
| * @param multimap the multimap whose contents are copied to this multimap |
| */ |
| public static <K, V> ArrayListMultimap<K, V> create( |
| Multimap<? extends K, ? extends V> multimap) { |
| return new ArrayListMultimap<K, V>(multimap); |
| } |
| |
| private ArrayListMultimap() { |
| super(new HashMap<K, Collection<V>>()); |
| expectedValuesPerKey = DEFAULT_VALUES_PER_KEY; |
| } |
| |
| private ArrayListMultimap(int expectedKeys, int expectedValuesPerKey) { |
| super(Maps.<K, Collection<V>>newHashMapWithExpectedSize(expectedKeys)); |
| checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey"); |
| this.expectedValuesPerKey = expectedValuesPerKey; |
| } |
| |
| private ArrayListMultimap(Multimap<? extends K, ? extends V> multimap) { |
| this(multimap.keySet().size(), |
| (multimap instanceof ArrayListMultimap) ? |
| ((ArrayListMultimap<?, ?>) multimap).expectedValuesPerKey : |
| DEFAULT_VALUES_PER_KEY); |
| putAll(multimap); |
| } |
| |
| /** |
| * Creates a new, empty {@code ArrayList} to hold the collection of values for |
| * an arbitrary key. |
| */ |
| @Override List<V> createCollection() { |
| return new ArrayList<V>(expectedValuesPerKey); |
| } |
| |
| /** |
| * Reduces the memory used by this {@code ArrayListMultimap}, if feasible. |
| */ |
| public void trimToSize() { |
| for (Collection<V> collection : backingMap().values()) { |
| ArrayList<V> arrayList = (ArrayList<V>) collection; |
| arrayList.trimToSize(); |
| } |
| } |
| } |
| |