com.google.common.collect.ArrayListMultimap Maven / Gradle / Ivy
/*
* 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.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;
import org.checkerframework.checker.nullness.qual.Nullable;
/**
* 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
*/
@GwtCompatible(serializable = true, emulated = true)
@ElementTypesAreNonnullByDefault
public final class ArrayListMultimap
extends ArrayListMultimapGwtSerializationDependencies {
// 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.
*
* This method will soon be deprecated in favor of {@code
* MultimapBuilder.hashKeys().arrayListValues().build()}.
*/
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.
*
* This method will soon be deprecated in favor of {@code
* MultimapBuilder.hashKeys(expectedKeys).arrayListValues(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
ArrayListMultimap create(int expectedKeys, int expectedValuesPerKey) {
return new ArrayListMultimap<>(expectedKeys, expectedValuesPerKey);
}
/**
* Constructs an {@code ArrayListMultimap} with the same mappings as the specified multimap.
*
* This method will soon be deprecated in favor of {@code
* MultimapBuilder.hashKeys().arrayListValues().build(multimap)}.
*
* @param multimap the multimap whose contents are copied to this multimap
*/
public static
ArrayListMultimap create(Multimap multimap) {
return new ArrayListMultimap<>(multimap);
}
private ArrayListMultimap() {
this(12, DEFAULT_VALUES_PER_KEY);
}
private ArrayListMultimap(int expectedKeys, int expectedValuesPerKey) {
super(Platform.>newHashMapWithExpectedSize(expectedKeys));
checkNonnegative(expectedValuesPerKey, "expectedValuesPerKey");
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.
*
* @deprecated For a {@link ListMultimap} that automatically trims to size, use {@link
* ImmutableListMultimap}. If you need a mutable collection, remove the {@code trimToSize}
* call, or switch to a {@code HashMap>}.
*/
@Deprecated
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();
Serialization.writeMultimap(this, stream);
}
@GwtIncompatible // java.io.ObjectOutputStream
private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
stream.defaultReadObject();
expectedValuesPerKey = DEFAULT_VALUES_PER_KEY;
int distinctKeys = Serialization.readCount(stream);
Map> map = Maps.newHashMap();
setMap(map);
Serialization.populateMultimap(this, stream, distinctKeys);
}
@GwtIncompatible // Not needed in emulated source.
private static final long serialVersionUID = 0;
}