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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 static com.google.common.base.Preconditions.checkArgument;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.VisibleForTesting;

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

/**
 * 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.
 *
 * 

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. * *

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. * *

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

The lists returned by {@link #get}, {@link #removeAll}, and {@link * #replaceValues} all implement {@link java.util.RandomAccess}. * *

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}. * *

See the Guava User Guide article on * {@code Multimap}. * * @author Jared Levy * @since 2.0 (imported from Google Collections Library) */ @GwtCompatible(serializable = true, emulated = true) public final class ArrayListMultimap extends AbstractListMultimap { // 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 ArrayListMultimap create() { return new ArrayListMultimap(); } /** * 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 ArrayListMultimap create( int expectedKeys, int expectedValuesPerKey) { return new ArrayListMultimap(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 ArrayListMultimap create( Multimap multimap) { return new ArrayListMultimap(multimap); } private ArrayListMultimap() { super(new HashMap>()); expectedValuesPerKey = DEFAULT_VALUES_PER_KEY; } private ArrayListMultimap(int expectedKeys, int expectedValuesPerKey) { super(Maps.>newHashMapWithExpectedSize(expectedKeys)); checkArgument(expectedValuesPerKey >= 0); this.expectedValuesPerKey = expectedValuesPerKey; } private ArrayListMultimap(Multimap 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 createCollection() { return new ArrayList(expectedValuesPerKey); } /** * Reduces the memory used by this {@code ArrayListMultimap}, if feasible. */ public void trimToSize() { for (Collection collection : backingMap().values()) { ArrayList arrayList = (ArrayList) collection; arrayList.trimToSize(); } } /** * @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.ObjectOutputStream") 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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