001/*
002 * Copyright (C) 2007 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.collect;
018
019import com.google.common.annotations.GwtCompatible;
020
021/**
022 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements
023 * according to when the first occurrence of the element was added. When the multiset contains
024 * multiple instances of an element, those instances are consecutive in the iteration order. If all
025 * occurrences of an element are removed, after which that element is added to the multiset, the
026 * element will appear at the end of the iteration.
027 *
028 * <p>See the Guava User Guide article on <a href=
029 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset"> {@code
030 * Multiset}</a>.
031 *
032 * @author Kevin Bourrillion
033 * @author Jared Levy
034 * @since 2.0
035 */
036@GwtCompatible(serializable = true, emulated = true)
037@SuppressWarnings("serial") // we're overriding default serialization
038public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> {
039
040  /** Creates a new, empty {@code LinkedHashMultiset} using the default initial capacity. */
041  public static <E> LinkedHashMultiset<E> create() {
042    return create(ObjectCountHashMap.DEFAULT_SIZE);
043  }
044
045  /**
046   * Creates a new, empty {@code LinkedHashMultiset} with the specified expected number of distinct
047   * elements.
048   *
049   * @param distinctElements the expected number of distinct elements
050   * @throws IllegalArgumentException if {@code distinctElements} is negative
051   */
052  public static <E> LinkedHashMultiset<E> create(int distinctElements) {
053    return new LinkedHashMultiset<E>(distinctElements);
054  }
055
056  /**
057   * Creates a new {@code LinkedHashMultiset} containing the specified elements.
058   *
059   * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}.
060   *
061   * @param elements the elements that the multiset should contain
062   */
063  public static <E> LinkedHashMultiset<E> create(Iterable<? extends E> elements) {
064    LinkedHashMultiset<E> multiset = create(Multisets.inferDistinctElements(elements));
065    Iterables.addAll(multiset, elements);
066    return multiset;
067  }
068
069  LinkedHashMultiset(int distinctElements) {
070    super(distinctElements);
071  }
072
073  @Override
074  void init(int distinctElements) {
075    backingMap = new ObjectCountLinkedHashMap<>(distinctElements);
076  }
077}