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 * @author Kevin Bourrillion 36 * @author Jared Levy 37 * @since 2.0 (imported from Google Collections Library) 38 */ 39 @GwtCompatible(serializable = true, emulated = true) 40 @SuppressWarnings("serial") // we're overriding default serialization 41 public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> { 42 43 /** 44 * Creates a new, empty {@code LinkedHashMultiset} using the default initial 45 * capacity. 46 */ 47 public static <E> LinkedHashMultiset<E> create() { 48 return new LinkedHashMultiset<E>(); 49 } 50 51 /** 52 * Creates a new, empty {@code LinkedHashMultiset} with the specified expected 53 * number of distinct elements. 54 * 55 * @param distinctElements the expected number of distinct elements 56 * @throws IllegalArgumentException if {@code distinctElements} is negative 57 */ 58 public static <E> LinkedHashMultiset<E> create(int distinctElements) { 59 return new LinkedHashMultiset<E>(distinctElements); 60 } 61 62 /** 63 * Creates a new {@code LinkedHashMultiset} containing the specified elements. 64 * 65 * <p>This implementation is highly efficient when {@code elements} is itself 66 * a {@link Multiset}. 67 * 68 * @param elements the elements that the multiset should contain 69 */ 70 public static <E> LinkedHashMultiset<E> create( 71 Iterable<? extends E> elements) { 72 LinkedHashMultiset<E> multiset = 73 create(Multisets.inferDistinctElements(elements)); 74 Iterables.addAll(multiset, elements); 75 return multiset; 76 } 77 78 private LinkedHashMultiset() { 79 super(new LinkedHashMap<E, Count>()); 80 } 81 82 private LinkedHashMultiset(int distinctElements) { 83 // Could use newLinkedHashMapWithExpectedSize() if it existed 84 super(new LinkedHashMap<E, Count>(Maps.capacity(distinctElements))); 85 } 86 87 /** 88 * @serialData the number of distinct elements, the first element, its count, 89 * the second element, its count, and so on 90 */ 91 @GwtIncompatible("java.io.ObjectOutputStream") 92 private void writeObject(ObjectOutputStream stream) throws IOException { 93 stream.defaultWriteObject(); 94 Serialization.writeMultiset(this, stream); 95 } 96 97 @GwtIncompatible("java.io.ObjectInputStream") 98 private void readObject(ObjectInputStream stream) 99 throws IOException, ClassNotFoundException { 100 stream.defaultReadObject(); 101 int distinctElements = Serialization.readCount(stream); 102 setBackingMap(new LinkedHashMap<E, Count>( 103 Maps.capacity(distinctElements))); 104 Serialization.populateMultiset(this, stream, distinctElements); 105 } 106 107 @GwtIncompatible("not needed in emulated source") 108 private static final long serialVersionUID = 0; 109 } 110
