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/*
* Copyright (C) 2007 Google Inc.
*
* 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.VisibleForTesting;
import static com.google.common.base.Preconditions.checkArgument;
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}.
*
* @author Jared Levy
*/
@GwtCompatible
public final class ArrayListMultimap extends StandardListMultimap {
// Default from ArrayList
private static final int DEFAULT_VALUES_PER_KEY = 10;
@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);
}
/** Constructs an empty {@code ArrayListMultimap}. */
private ArrayListMultimap() {
super(new HashMap>());
expectedValuesPerKey = DEFAULT_VALUES_PER_KEY;
}
/**
* Constructs an empty {@code ArrayListMultimap} with the expected number of
* distinct keys and the expected number of values per distinct key.
*
* @param expectedKeys the expected number of distinct keys
* @param expectedValuesPerKey the expected average number of values per key
* @throws IllegalArgumentException if either argument is negative
*/
private ArrayListMultimap(int expectedKeys, int expectedValuesPerKey) {
super(Maps.>newHashMapWithExpectedSize(expectedKeys));
checkArgument(expectedValuesPerKey >= 0);
this.expectedValuesPerKey = expectedValuesPerKey;
}
/**
* Constructs an {@code ArrayListMultimap} with the same mappings as the
* specified multimap.
*/
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
*/
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
stream.writeInt(expectedValuesPerKey);
Serialization.writeMultimap(this, stream);
}
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);
}
private static final long serialVersionUID = 0;
}