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Google Collections Library is a suite of new collections and collection-related goodness for Java 5.0

There is a newer version: 1.0

/*
 * 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 static com.google.common.base.Preconditions.checkArgument;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.EnumMap;
import java.util.Iterator;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * Multiset implementation backed by an {@link EnumMap}.
 *
 * @author Jared Levy
 */
public final class EnumMultiset>
    extends AbstractMapBasedMultiset {
  private transient Class type;
  
  /** Creates an empty {@code EnumMultiset}. */
  public EnumMultiset(Class type) {
    super(new EnumMap(type));
    this.type = type;
  }

  /**
   * Creates a new {@code EnumMultiset} containing the specified elements.
   *
   * @param elements the elements that the multiset should contain
   * @throws IllegalArgumentException if {@code elements} is empty
   */
  public EnumMultiset(Iterable elements) {
    this(findClass(elements));
    Iterables.addAll(this, elements);
  }

  /**
   * Determine the class of the first element in an {@link Iterable}.
   *
   * @param elements the elements to examine
   * @return the {@link Class} of the first element
   * @throws IllegalArgumentException if {@code elements} is empty
   */
  private static > Class findClass(Iterable elements) {
    Iterator iterator = elements.iterator();
    checkArgument(iterator.hasNext(),
        "EnumMultiset constructor passed empty Iterable");
    return iterator.next().getDeclaringClass();
  }

  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    stream.writeObject(type);
    Serialization.writeMultiset(this, stream);
  }
  
  /**
   * @serialData the {@code Class} for the enum type, the number of distinct
   *    elements, the first element, its count, the second element, its count,
   *    and so on
   */
  private void readObject(ObjectInputStream stream)
      throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    @SuppressWarnings("unchecked") // reading data stored by writeObject
    Class localType = (Class) stream.readObject();
    type = localType;
    setBackingMap(new EnumMap(type));
    Serialization.populateMultiset(this, stream);
  }  
  
  private static final long serialVersionUID = 0;  
}