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 org.checkerframework.checker.nullness.qual.Nullable; 021 022/** 023 * A {@code Multiset} implementation with predictable iteration order. Its iterator orders elements 024 * according to when the first occurrence of the element was added. When the multiset contains 025 * multiple instances of an element, those instances are consecutive in the iteration order. If all 026 * occurrences of an element are removed, after which that element is added to the multiset, the 027 * element will appear at the end of the iteration. 028 * 029 * <p>See the Guava User Guide article on <a href= 030 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset">{@code Multiset}</a>. 031 * 032 * @author Kevin Bourrillion 033 * @author Jared Levy 034 * @since 2.0 035 */ 036@GwtCompatible(serializable = true, emulated = true) 037@ElementTypesAreNonnullByDefault 038public final class LinkedHashMultiset<E extends @Nullable Object> 039 extends AbstractMapBasedMultiset<E> { 040 041 /** Creates a new, empty {@code LinkedHashMultiset} using the default initial capacity. */ 042 public static <E extends @Nullable Object> LinkedHashMultiset<E> create() { 043 return create(ObjectCountHashMap.DEFAULT_SIZE); 044 } 045 046 /** 047 * Creates a new, empty {@code LinkedHashMultiset} with the specified expected number of distinct 048 * elements. 049 * 050 * @param distinctElements the expected number of distinct elements 051 * @throws IllegalArgumentException if {@code distinctElements} is negative 052 */ 053 public static <E extends @Nullable Object> LinkedHashMultiset<E> create(int distinctElements) { 054 return new LinkedHashMultiset<E>(distinctElements); 055 } 056 057 /** 058 * Creates a new {@code LinkedHashMultiset} containing the specified elements. 059 * 060 * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}. 061 * 062 * @param elements the elements that the multiset should contain 063 */ 064 public static <E extends @Nullable Object> LinkedHashMultiset<E> create( 065 Iterable<? extends E> elements) { 066 LinkedHashMultiset<E> multiset = create(Multisets.inferDistinctElements(elements)); 067 Iterables.addAll(multiset, elements); 068 return multiset; 069 } 070 071 LinkedHashMultiset(int distinctElements) { 072 super(distinctElements); 073 } 074 075 @Override 076 ObjectCountHashMap<E> newBackingMap(int distinctElements) { 077 return new ObjectCountLinkedHashMap<>(distinctElements); 078 } 079}