| /* |
| * 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 com.google.common.annotations.GwtCompatible; |
| import com.google.common.annotations.GwtIncompatible; |
| import com.google.common.annotations.VisibleForTesting; |
| import com.google.common.base.Preconditions; |
| import java.io.IOException; |
| import java.io.ObjectInputStream; |
| import java.io.ObjectOutputStream; |
| import java.util.Collection; |
| import java.util.Map; |
| import java.util.Set; |
| |
| /** |
| * Implementation of {@link Multimap} using hash tables. |
| * |
| * <p>The multimap does not store duplicate key-value pairs. Adding a new key-value pair equal to an |
| * existing key-value pair has no effect. |
| * |
| * <p>Keys and values may be null. All optional multimap methods are supported, and all returned |
| * views are modifiable. |
| * |
| * <p>This class is not threadsafe when any concurrent operations update the multimap. Concurrent |
| * read operations will work correctly if the last write <i>happens-before</i> any reads. To allow |
| * concurrent update operations, wrap your multimap with a call to {@link |
| * Multimaps#synchronizedSetMultimap}. |
| * |
| * @author Jared Levy |
| * @since 2.0 |
| */ |
| @GwtCompatible(serializable = true, emulated = true) |
| public final class HashMultimap<K, V> extends HashMultimapGwtSerializationDependencies<K, V> { |
| private static final int DEFAULT_VALUES_PER_KEY = 2; |
| |
| @VisibleForTesting transient int expectedValuesPerKey = DEFAULT_VALUES_PER_KEY; |
| |
| /** |
| * Creates a new, empty {@code HashMultimap} with the default initial capacities. |
| * |
| * <p>This method will soon be deprecated in favor of {@code |
| * MultimapBuilder.hashKeys().hashSetValues().build()}. |
| */ |
| public static <K, V> HashMultimap<K, V> create() { |
| return new HashMultimap<>(); |
| } |
| |
| /** |
| * Constructs an empty {@code HashMultimap} with enough capacity to hold the specified numbers of |
| * keys and values without rehashing. |
| * |
| * <p>This method will soon be deprecated in favor of {@code |
| * MultimapBuilder.hashKeys(expectedKeys).hashSetValues(expectedValuesPerKey).build()}. |
| * |
| * @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> HashMultimap<K, V> create(int expectedKeys, int expectedValuesPerKey) { |
| return new HashMultimap<>(expectedKeys, expectedValuesPerKey); |
| } |
| |
| /** |
| * Constructs a {@code HashMultimap} with the same mappings as the specified multimap. If a |
| * key-value mapping appears multiple times in the input multimap, it only appears once in the |
| * constructed multimap. |
| * |
| * <p>This method will soon be deprecated in favor of {@code |
| * MultimapBuilder.hashKeys().hashSetValues().build(multimap)}. |
| * |
| * @param multimap the multimap whose contents are copied to this multimap |
| */ |
| public static <K, V> HashMultimap<K, V> create(Multimap<? extends K, ? extends V> multimap) { |
| return new HashMultimap<>(multimap); |
| } |
| |
| private HashMultimap() { |
| this(12, DEFAULT_VALUES_PER_KEY); |
| } |
| |
| private HashMultimap(int expectedKeys, int expectedValuesPerKey) { |
| super(Platform.<K, Collection<V>>newHashMapWithExpectedSize(expectedKeys)); |
| Preconditions.checkArgument(expectedValuesPerKey >= 0); |
| this.expectedValuesPerKey = expectedValuesPerKey; |
| } |
| |
| private HashMultimap(Multimap<? extends K, ? extends V> multimap) { |
| super(Platform.<K, Collection<V>>newHashMapWithExpectedSize(multimap.keySet().size())); |
| putAll(multimap); |
| } |
| |
| /** |
| * {@inheritDoc} |
| * |
| * <p>Creates an empty {@code HashSet} for a collection of values for one key. |
| * |
| * @return a new {@code HashSet} containing a collection of values for one key |
| */ |
| @Override |
| Set<V> createCollection() { |
| return Platform.<V>newHashSetWithExpectedSize(expectedValuesPerKey); |
| } |
| |
| /** |
| * @serialData expectedValuesPerKey, number of distinct keys, and then for each distinct key: the |
| * key, number of values for that key, and the key's values |
| */ |
| @GwtIncompatible // java.io.ObjectOutputStream |
| private void writeObject(ObjectOutputStream stream) throws IOException { |
| stream.defaultWriteObject(); |
| Serialization.writeMultimap(this, stream); |
| } |
| |
| @GwtIncompatible // java.io.ObjectInputStream |
| private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { |
| stream.defaultReadObject(); |
| expectedValuesPerKey = DEFAULT_VALUES_PER_KEY; |
| int distinctKeys = Serialization.readCount(stream); |
| Map<K, Collection<V>> map = Platform.newHashMapWithExpectedSize(12); |
| setMap(map); |
| Serialization.populateMultimap(this, stream, distinctKeys); |
| } |
| |
| @GwtIncompatible // Not needed in emulated source |
| private static final long serialVersionUID = 0; |
| } |