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 21 /** 22 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements 23 * according to when the first occurrence of the element was added. When the multiset contains 24 * multiple instances of an element, those instances are consecutive in the iteration order. If all 25 * occurrences of an element are removed, after which that element is added to the multiset, the 26 * element will appear at the end of the iteration. 27 * 28 * <p>See the Guava User Guide article on <a href= 29 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset"> {@code 30 * Multiset}</a>. 31 * 32 * @author Kevin Bourrillion 33 * @author Jared Levy 34 * @since 2.0 35 */ 36 @GwtCompatible(serializable = true, emulated = true) 37 public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> { 38 39 /** Creates a new, empty {@code LinkedHashMultiset} using the default initial capacity. */ create()40 public static <E> LinkedHashMultiset<E> create() { 41 return create(ObjectCountHashMap.DEFAULT_SIZE); 42 } 43 44 /** 45 * Creates a new, empty {@code LinkedHashMultiset} with the specified expected number of distinct 46 * elements. 47 * 48 * @param distinctElements the expected number of distinct elements 49 * @throws IllegalArgumentException if {@code distinctElements} is negative 50 */ create(int distinctElements)51 public static <E> LinkedHashMultiset<E> create(int distinctElements) { 52 return new LinkedHashMultiset<E>(distinctElements); 53 } 54 55 /** 56 * Creates a new {@code LinkedHashMultiset} containing the specified elements. 57 * 58 * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}. 59 * 60 * @param elements the elements that the multiset should contain 61 */ create(Iterable<? extends E> elements)62 public static <E> LinkedHashMultiset<E> create(Iterable<? extends E> elements) { 63 LinkedHashMultiset<E> multiset = create(Multisets.inferDistinctElements(elements)); 64 Iterables.addAll(multiset, elements); 65 return multiset; 66 } 67 LinkedHashMultiset(int distinctElements)68 LinkedHashMultiset(int distinctElements) { 69 super(distinctElements); 70 } 71 72 @Override init(int distinctElements)73 void init(int distinctElements) { 74 backingMap = new ObjectCountLinkedHashMap<>(distinctElements); 75 } 76 } 77