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

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

/**
 * Multiset implementation backed by an {@link EnumMap}.
 *
 * @author Jared Levy
 */
@SuppressWarnings("serial") // we're overriding default serialization
public final class EnumMultiset>
    extends AbstractMapBasedMultiset {
  private final 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 static class SerializedForm>
      extends MultisetSerializedForm {
    private final Class type;    
    SerializedForm(EnumMultiset multiset) {
      super(multiset);
      this.type = multiset.type;
    }
    @Override protected Multiset createEmpty() {
      return new EnumMultiset(type);
    }
    private static final long serialVersionUID = 0;
  }

  private void readObject(ObjectInputStream stream)
      throws InvalidObjectException {
    throw new InvalidObjectException("Use SerializedForm");
  }

  private Object writeReplace() {
    return new SerializedForm(this);
  }
}