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 031 * Multiset}</a>. 032 * 033 * @author Kevin Bourrillion 034 * @author Jared Levy 035 * @since 2.0 036 */ 037@GwtCompatible(serializable = true, emulated = true) 038@ElementTypesAreNonnullByDefault 039public final class LinkedHashMultiset<E extends @Nullable Object> 040 extends AbstractMapBasedMultiset<E> { 041 042 /** Creates a new, empty {@code LinkedHashMultiset} using the default initial capacity. */ 043 public static <E extends @Nullable Object> LinkedHashMultiset<E> create() { 044 return create(ObjectCountHashMap.DEFAULT_SIZE); 045 } 046 047 /** 048 * Creates a new, empty {@code LinkedHashMultiset} with the specified expected number of distinct 049 * elements. 050 * 051 * @param distinctElements the expected number of distinct elements 052 * @throws IllegalArgumentException if {@code distinctElements} is negative 053 */ 054 public static <E extends @Nullable Object> LinkedHashMultiset<E> create(int distinctElements) { 055 return new LinkedHashMultiset<E>(distinctElements); 056 } 057 058 /** 059 * Creates a new {@code LinkedHashMultiset} containing the specified elements. 060 * 061 * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}. 062 * 063 * @param elements the elements that the multiset should contain 064 */ 065 public static <E extends @Nullable Object> LinkedHashMultiset<E> create( 066 Iterable<? extends E> elements) { 067 LinkedHashMultiset<E> multiset = create(Multisets.inferDistinctElements(elements)); 068 Iterables.addAll(multiset, elements); 069 return multiset; 070 } 071 072 LinkedHashMultiset(int distinctElements) { 073 super(distinctElements); 074 } 075 076 @Override 077 ObjectCountHashMap<E> newBackingMap(int distinctElements) { 078 return new ObjectCountLinkedHashMap<>(distinctElements); 079 } 080}