/*
* 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 java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.HashMap;
/**
* Multiset implementation backed by a {@link HashMap}.
*
* @author Kevin Bourrillion
* @author Jared Levy
* @since 2.0 (imported from Google Collections Library)
*/
@GwtCompatible(serializable = true, emulated = true)
public final class HashMultiset<E> extends AbstractMapBasedMultiset<E> {
/**
* Creates a new, empty {@code HashMultiset} using the default initial
* capacity.
*/
public static <E> HashMultiset<E> create() {
return new HashMultiset<E>();
}
/**
* Creates a new, empty {@code HashMultiset} with the specified expected
* number of distinct elements.
*
* @param distinctElements the expected number of distinct elements
* @throws IllegalArgumentException if {@code distinctElements} is negative
*/
public static <E> HashMultiset<E> create(int distinctElements) {
return new HashMultiset<E>(distinctElements);
}
/**
* Creates a new {@code HashMultiset} containing the specified elements.
*
* <p>This implementation is highly efficient when {@code elements} is itself
* a {@link Multiset}.
*
* @param elements the elements that the multiset should contain
*/
public static <E> HashMultiset<E> create(Iterable<? extends E> elements) {
HashMultiset<E> multiset =
create(Multisets.inferDistinctElements(elements));
Iterables.addAll(multiset, elements);
return multiset;
}
private HashMultiset() {
super(new HashMap<E, Count>());
}
private HashMultiset(int distinctElements) {
super(Maps.<E, Count>newHashMapWithExpectedSize(distinctElements));
}
/**
* @serialData the number of distinct elements, the first element, its count,
* the second element, its count, and so on
*/
@GwtIncompatible("java.io.ObjectOutputStream")
private void writeObject(ObjectOutputStream stream) throws IOException {
stream.defaultWriteObject();
Serialization.writeMultiset(this, stream);
}
@GwtIncompatible("java.io.ObjectInputStream")
private void readObject(ObjectInputStream stream)
throws IOException, ClassNotFoundException {
stream.defaultReadObject();
int distinctElements = Serialization.readCount(stream);
setBackingMap(
Maps.<E, Count>newHashMapWithExpectedSize(distinctElements));
Serialization.populateMultiset(this, stream, distinctElements);
}
@GwtIncompatible("Not needed in emulated source.")
private static final long serialVersionUID = 0;
}
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