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/*
 * 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.HashMap;
import java.util.Map;
import java.util.Set;

/**
 * Implementation of {@link Multimap} using hash tables.
 *
 * 

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. * *

Keys and values may be null. All optional multimap methods are supported, * and all returned views are modifiable. * *

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#synchronizedSetMultimap}. * * @author Jared Levy * @since 2.0 (imported from Google Collections Library) */ @GwtCompatible(serializable = true, emulated = true) public final class HashMultimap extends AbstractSetMultimap { 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. */ public static HashMultimap create() { return new HashMultimap(); } /** * Constructs an empty {@code HashMultimap} with enough capacity to hold the * specified numbers of keys and values without rehashing. * * @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 HashMultimap 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. * * @param multimap the multimap whose contents are copied to this multimap */ public static HashMultimap create( Multimap multimap) { return new HashMultimap(multimap); } private HashMultimap() { super(new HashMap>()); } private HashMultimap(int expectedKeys, int expectedValuesPerKey) { super(Maps.>newHashMapWithExpectedSize(expectedKeys)); Preconditions.checkArgument(expectedValuesPerKey >= 0); this.expectedValuesPerKey = expectedValuesPerKey; } private HashMultimap(Multimap multimap) { super(Maps.>newHashMapWithExpectedSize( multimap.keySet().size())); putAll(multimap); } /** * {@inheritDoc} * *

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 createCollection() { return Sets.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(); stream.writeInt(expectedValuesPerKey); Serialization.writeMultimap(this, stream); } @GwtIncompatible("java.io.ObjectInputStream") private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { stream.defaultReadObject(); expectedValuesPerKey = stream.readInt(); int distinctKeys = Serialization.readCount(stream); Map> map = Maps.newHashMapWithExpectedSize(distinctKeys); setMap(map); Serialization.populateMultimap(this, stream, distinctKeys); } @GwtIncompatible("Not needed in emulated source") private static final long serialVersionUID = 0; }





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