144 lines
4.9 KiB
Java
144 lines
4.9 KiB
Java
/*
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* Copyright (C) 2007 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.common.collect;
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import java.io.IOException;
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import java.io.ObjectInputStream;
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import java.io.ObjectOutputStream;
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import java.util.Collection;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.Set;
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import com.google.common.annotations.GwtCompatible;
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import com.google.common.annotations.GwtIncompatible;
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import com.google.common.annotations.VisibleForTesting;
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import com.google.common.base.Preconditions;
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/**
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* Implementation of {@link Multimap} using hash tables.
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*
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* <p>
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* The multimap does not store duplicate key-value pairs. Adding a new key-value
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* pair equal to an existing key-value pair has no effect.
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*
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* <p>
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* Keys and values may be null. All optional multimap methods are supported, and
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* all returned views are modifiable.
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*
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* <p>
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* This class is not threadsafe when any concurrent operations update the
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* multimap. Concurrent read operations will work correctly. To allow concurrent
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* update operations, wrap your multimap with a call to
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* {@link Multimaps#synchronizedSetMultimap}.
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*
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* @author Jared Levy
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* @since 2.0 (imported from Google Collections Library)
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*/
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@GwtCompatible(serializable = true, emulated = true)
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public final class HashMultimap<K, V> extends AbstractSetMultimap<K, V> {
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private static final int DEFAULT_VALUES_PER_KEY = 2;
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@VisibleForTesting
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transient int expectedValuesPerKey = DEFAULT_VALUES_PER_KEY;
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/**
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* Creates a new, empty {@code HashMultimap} with the default initial
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* capacities.
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*/
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public static <K, V> HashMultimap<K, V> create() {
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return new HashMultimap<K, V>();
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}
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/**
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* Constructs an empty {@code HashMultimap} with enough capacity to hold the
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* specified numbers of keys and values without rehashing.
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*
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* @param expectedKeys the expected number of distinct keys
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* @param expectedValuesPerKey the expected average number of values per key
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* @throws IllegalArgumentException if {@code expectedKeys} or {@code
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* expectedValuesPerKey} is negative
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*/
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public static <K, V> HashMultimap<K, V> create(int expectedKeys, int expectedValuesPerKey) {
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return new HashMultimap<K, V>(expectedKeys, expectedValuesPerKey);
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}
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/**
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* Constructs a {@code HashMultimap} with the same mappings as the specified
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* multimap. If a key-value mapping appears multiple times in the input
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* multimap, it only appears once in the constructed multimap.
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*
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* @param multimap the multimap whose contents are copied to this multimap
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*/
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public static <K, V> HashMultimap<K, V> create(Multimap<? extends K, ? extends V> multimap) {
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return new HashMultimap<K, V>(multimap);
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}
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private HashMultimap() {
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super(new HashMap<K, Collection<V>>());
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}
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private HashMultimap(int expectedKeys, int expectedValuesPerKey) {
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super(Maps.<K, Collection<V>>newHashMapWithExpectedSize(expectedKeys));
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Preconditions.checkArgument(expectedValuesPerKey >= 0);
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this.expectedValuesPerKey = expectedValuesPerKey;
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}
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private HashMultimap(Multimap<? extends K, ? extends V> multimap) {
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super(Maps.<K, Collection<V>>newHashMapWithExpectedSize(multimap.keySet().size()));
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putAll(multimap);
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}
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/**
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* {@inheritDoc}
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*
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* <p>
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* Creates an empty {@code HashSet} for a collection of values for one key.
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*
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* @return a new {@code HashSet} containing a collection of values for one key
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*/
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@Override
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Set<V> createCollection() {
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return Sets.<V>newHashSetWithExpectedSize(expectedValuesPerKey);
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}
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/**
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* @serialData expectedValuesPerKey, number of distinct keys, and then for each
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* distinct key: the key, number of values for that key, and the
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* key's values
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*/
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@GwtIncompatible("java.io.ObjectOutputStream")
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private void writeObject(ObjectOutputStream stream) throws IOException {
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stream.defaultWriteObject();
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stream.writeInt(expectedValuesPerKey);
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Serialization.writeMultimap(this, stream);
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}
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@GwtIncompatible("java.io.ObjectInputStream")
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private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
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stream.defaultReadObject();
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expectedValuesPerKey = stream.readInt();
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int distinctKeys = Serialization.readCount(stream);
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Map<K, Collection<V>> map = Maps.newHashMapWithExpectedSize(distinctKeys);
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setMap(map);
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Serialization.populateMultimap(this, stream, distinctKeys);
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}
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@GwtIncompatible("Not needed in emulated source")
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private static final long serialVersionUID = 0;
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}
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