com.google.common.collect.HashMultiset.java Source code

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Here is the source code for com.google.common.collect.HashMultiset.java

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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 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
 */
@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>newHashMap());
        Serialization.populateMultiset(this, stream, distinctElements);
    }

    @GwtIncompatible("Not needed in emulated source.")
    private static final long serialVersionUID = 0;
}