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 17 package com.google.common.collect; 18 19 import com.google.common.annotations.GwtCompatible; 20 import com.google.common.annotations.GwtIncompatible; 21 22 import java.io.IOException; 23 import java.io.ObjectInputStream; 24 import java.io.ObjectOutputStream; 25 import 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 45 public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> { 46 47 /** 48 * Creates a new, empty {@code LinkedHashMultiset} using the default initial 49 * capacity. 50 */ create()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 */ create(int distinctElements)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 */ create( Iterable<? extends E> elements)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 LinkedHashMultiset()82 private LinkedHashMultiset() { 83 super(new LinkedHashMap<E, Count>()); 84 } 85 LinkedHashMultiset(int distinctElements)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") writeObject(ObjectOutputStream stream)96 private void writeObject(ObjectOutputStream stream) throws IOException { 97 stream.defaultWriteObject(); 98 Serialization.writeMultiset(this, stream); 99 } 100 101 @GwtIncompatible("java.io.ObjectInputStream") readObject(ObjectInputStream stream)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