LinkedHashMultiset.java revision 0888a09821a98ac0680fad765217302858e70fa4 
1/*
2 * Copyright (C) 2007 The Guava Authors
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.google.common.collect;
18
19import com.google.common.annotations.GwtCompatible;
20import com.google.common.annotations.GwtIncompatible;
21
22import java.io.IOException;
23import java.io.ObjectInputStream;
24import java.io.ObjectOutputStream;
25import java.util.LinkedHashMap;
26
27/**
28 * A {@code Multiset} implementation with predictable iteration order. Its
29 * iterator orders elements according to when the first occurrence of the
30 * element was added. When the multiset contains multiple instances of an
31 * element, those instances are consecutive in the iteration order. If all
32 * occurrences of an element are removed, after which that element is added to
33 * the multiset, the element will appear at the end of the iteration.
34 *
35 * <p>See the Guava User Guide article on <a href=
36 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multiset">
37 * {@code Multiset}</a>.
38 *
39 * @author Kevin Bourrillion
40 * @author Jared Levy
41 * @since 2.0 (imported from Google Collections Library)
42 */
43@GwtCompatible(serializable = true, emulated = true)
44@SuppressWarnings("serial") // we're overriding default serialization
45public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> {
46
47  /**
48   * Creates a new, empty {@code LinkedHashMultiset} using the default initial
49   * capacity.
50   */
51  public static <E> LinkedHashMultiset<E> create() {
52    return new LinkedHashMultiset<E>();
53  }
54
55  /**
56   * Creates a new, empty {@code LinkedHashMultiset} with the specified expected
57   * number of distinct elements.
58   *
59   * @param distinctElements the expected number of distinct elements
60   * @throws IllegalArgumentException if {@code distinctElements} is negative
61   */
62  public static <E> LinkedHashMultiset<E> create(int distinctElements) {
63    return new LinkedHashMultiset<E>(distinctElements);
64  }
65
66  /**
67   * Creates a new {@code LinkedHashMultiset} containing the specified elements.
68   *
69   * <p>This implementation is highly efficient when {@code elements} is itself
70   * a {@link Multiset}.
71   *
72   * @param elements the elements that the multiset should contain
73   */
74  public static <E> LinkedHashMultiset<E> create(
75      Iterable<? extends E> elements) {
76    LinkedHashMultiset<E> multiset =
77        create(Multisets.inferDistinctElements(elements));
78    Iterables.addAll(multiset, elements);
79    return multiset;
80  }
81
82  private LinkedHashMultiset() {
83    super(new LinkedHashMap<E, Count>());
84  }
85
86  private LinkedHashMultiset(int distinctElements) {
87    // Could use newLinkedHashMapWithExpectedSize() if it existed
88    super(new LinkedHashMap<E, Count>(Maps.capacity(distinctElements)));
89  }
90
91  /**
92   * @serialData the number of distinct elements, the first element, its count,
93   *     the second element, its count, and so on
94   */
95  @GwtIncompatible("java.io.ObjectOutputStream")
96  private void writeObject(ObjectOutputStream stream) throws IOException {
97    stream.defaultWriteObject();
98    Serialization.writeMultiset(this, stream);
99  }
100
101  @GwtIncompatible("java.io.ObjectInputStream")
102  private void readObject(ObjectInputStream stream)
103      throws IOException, ClassNotFoundException {
104    stream.defaultReadObject();
105    int distinctElements = Serialization.readCount(stream);
106    setBackingMap(new LinkedHashMap<E, Count>(
107        Maps.capacity(distinctElements)));
108    Serialization.populateMultiset(this, stream, distinctElements);
109  }
110
111  @GwtIncompatible("not needed in emulated source")
112  private static final long serialVersionUID = 0;
113}
114