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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 java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
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
*/
public final class HashMultimap extends StandardSetMultimap {
/** Constructs an empty {@code HashMultimap}. */
public HashMultimap() {
super(new HashMap>());
}
/**
* Constructs a {@code HashMultimap} with the same mappings as the specified
* {@code 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.
* @see #putAll(Multimap)
*/
public HashMultimap(Multimap multimap) {
super(new HashMap>(
Maps.capacity(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 new HashSet();
}
private static final long serialVersionUID = 4309375142408689415L;
}