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; 020import com.google.common.annotations.GwtIncompatible; 021import java.io.IOException; 022import java.io.ObjectInputStream; 023import java.io.ObjectOutputStream; 024import java.util.LinkedHashMap; 025 026/** 027 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements 028 * according to when the first occurrence of the element was added. When the multiset contains 029 * multiple instances of an element, those instances are consecutive in the iteration order. If all 030 * occurrences of an element are removed, after which that element is added to the multiset, the 031 * element will appear at the end of the iteration. 032 * 033 * <p>See the Guava User Guide article on <a href= 034 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset"> {@code 035 * Multiset}</a>. 036 * 037 * @author Kevin Bourrillion 038 * @author Jared Levy 039 * @since 2.0 040 */ 041@GwtCompatible(serializable = true, emulated = true) 042public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> { 043 044 /** Creates a new, empty {@code LinkedHashMultiset} using the default initial capacity. */ 045 public static <E> LinkedHashMultiset<E> create() { 046 return new LinkedHashMultiset<E>(); 047 } 048 049 /** 050 * Creates a new, empty {@code LinkedHashMultiset} with the specified expected number of distinct 051 * elements. 052 * 053 * @param distinctElements the expected number of distinct elements 054 * @throws IllegalArgumentException if {@code distinctElements} is negative 055 */ 056 public static <E> LinkedHashMultiset<E> create(int distinctElements) { 057 return new LinkedHashMultiset<E>(distinctElements); 058 } 059 060 /** 061 * Creates a new {@code LinkedHashMultiset} containing the specified elements. 062 * 063 * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}. 064 * 065 * @param elements the elements that the multiset should contain 066 */ 067 public static <E> LinkedHashMultiset<E> create(Iterable<? extends E> elements) { 068 LinkedHashMultiset<E> multiset = create(Multisets.inferDistinctElements(elements)); 069 Iterables.addAll(multiset, elements); 070 return multiset; 071 } 072 073 private LinkedHashMultiset() { 074 super(new LinkedHashMap<E, Count>()); 075 } 076 077 private LinkedHashMultiset(int distinctElements) { 078 super(Maps.<E, Count>newLinkedHashMapWithExpectedSize(distinctElements)); 079 } 080 081 /** 082 * @serialData the number of distinct elements, the first element, its count, the second element, 083 * its count, and so on 084 */ 085 @GwtIncompatible // java.io.ObjectOutputStream 086 private void writeObject(ObjectOutputStream stream) throws IOException { 087 stream.defaultWriteObject(); 088 Serialization.writeMultiset(this, stream); 089 } 090 091 @GwtIncompatible // java.io.ObjectInputStream 092 private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException { 093 stream.defaultReadObject(); 094 int distinctElements = Serialization.readCount(stream); 095 setBackingMap(new LinkedHashMap<E, Count>()); 096 Serialization.populateMultiset(this, stream, distinctElements); 097 } 098 099 @GwtIncompatible // not needed in emulated source 100 private static final long serialVersionUID = 0; 101}