/*
    * 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;
 }