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
017 package com.google.common.collect;
018
019 import com.google.common.annotations.GwtCompatible;
020 import com.google.common.annotations.GwtIncompatible;
021
022 import java.io.IOException;
023 import java.io.ObjectInputStream;
024 import java.io.ObjectOutputStream;
025 import java.util.LinkedHashMap;
026
027 /**
028 * A {@code Multiset} implementation with predictable iteration order. Its
029 * iterator orders elements according to when the first occurrence of the
030 * element was added. When the multiset contains multiple instances of an
031 * element, those instances are consecutive in the iteration order. If all
032 * occurrences of an element are removed, after which that element is added to
033 * the multiset, the element will appear at the end of the iteration.
034 *
035 * <p>See the Guava User Guide article on <a href=
036 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multiset">
037 * {@code Multiset}</a>.
038 *
039 * @author Kevin Bourrillion
040 * @author Jared Levy
041 * @since 2.0 (imported from Google Collections Library)
042 */
043 @GwtCompatible(serializable = true, emulated = true)
044 @SuppressWarnings("serial") // we're overriding default serialization
045 public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> {
046
047 /**
048 * Creates a new, empty {@code LinkedHashMultiset} using the default initial
049 * capacity.
050 */
051 public static <E> LinkedHashMultiset<E> create() {
052 return new LinkedHashMultiset<E>();
053 }
054
055 /**
056 * Creates a new, empty {@code LinkedHashMultiset} with the specified expected
057 * number of distinct elements.
058 *
059 * @param distinctElements the expected number of distinct elements
060 * @throws IllegalArgumentException if {@code distinctElements} is negative
061 */
062 public static <E> LinkedHashMultiset<E> create(int distinctElements) {
063 return new LinkedHashMultiset<E>(distinctElements);
064 }
065
066 /**
067 * Creates a new {@code LinkedHashMultiset} containing the specified elements.
068 *
069 * <p>This implementation is highly efficient when {@code elements} is itself
070 * a {@link Multiset}.
071 *
072 * @param elements the elements that the multiset should contain
073 */
074 public static <E> LinkedHashMultiset<E> create(
075 Iterable<? extends E> elements) {
076 LinkedHashMultiset<E> multiset =
077 create(Multisets.inferDistinctElements(elements));
078 Iterables.addAll(multiset, elements);
079 return multiset;
080 }
081
082 private LinkedHashMultiset() {
083 super(new LinkedHashMap<E, Count>());
084 }
085
086 private LinkedHashMultiset(int distinctElements) {
087 // Could use newLinkedHashMapWithExpectedSize() if it existed
088 super(new LinkedHashMap<E, Count>(Maps.capacity(distinctElements)));
089 }
090
091 /**
092 * @serialData the number of distinct elements, the first element, its count,
093 * the second element, its count, and so on
094 */
095 @GwtIncompatible("java.io.ObjectOutputStream")
096 private void writeObject(ObjectOutputStream stream) throws IOException {
097 stream.defaultWriteObject();
098 Serialization.writeMultiset(this, stream);
099 }
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 }