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 17package com.google.common.collect; 18 19import com.google.common.annotations.GwtCompatible; 20import com.google.common.annotations.GwtIncompatible; 21 22import java.io.IOException; 23import java.io.ObjectInputStream; 24import java.io.ObjectOutputStream; 25import java.util.HashMap; 26 27/** 28 * Multiset implementation backed by a {@link HashMap}. 29 * 30 * @author Kevin Bourrillion 31 * @author Jared Levy 32 * @since 2.0 (imported from Google Collections Library) 33 */ 34@GwtCompatible(serializable = true, emulated = true) 35public final class HashMultiset<E> extends AbstractMapBasedMultiset<E> { 36 37 /** 38 * Creates a new, empty {@code HashMultiset} using the default initial 39 * capacity. 40 */ 41 public static <E> HashMultiset<E> create() { 42 return new HashMultiset<E>(); 43 } 44 45 /** 46 * Creates a new, empty {@code HashMultiset} with the specified expected 47 * number of distinct elements. 48 * 49 * @param distinctElements the expected number of distinct elements 50 * @throws IllegalArgumentException if {@code distinctElements} is negative 51 */ 52 public static <E> HashMultiset<E> create(int distinctElements) { 53 return new HashMultiset<E>(distinctElements); 54 } 55 56 /** 57 * Creates a new {@code HashMultiset} containing the specified elements. 58 * 59 * <p>This implementation is highly efficient when {@code elements} is itself 60 * a {@link Multiset}. 61 * 62 * @param elements the elements that the multiset should contain 63 */ 64 public static <E> HashMultiset<E> create(Iterable<? extends E> elements) { 65 HashMultiset<E> multiset = 66 create(Multisets.inferDistinctElements(elements)); 67 Iterables.addAll(multiset, elements); 68 return multiset; 69 } 70 71 private HashMultiset() { 72 super(new HashMap<E, Count>()); 73 } 74 75 private HashMultiset(int distinctElements) { 76 super(Maps.<E, Count>newHashMapWithExpectedSize(distinctElements)); 77 } 78 79 /** 80 * @serialData the number of distinct elements, the first element, its count, 81 * the second element, its count, and so on 82 */ 83 @GwtIncompatible("java.io.ObjectOutputStream") 84 private void writeObject(ObjectOutputStream stream) throws IOException { 85 stream.defaultWriteObject(); 86 Serialization.writeMultiset(this, stream); 87 } 88 89 @GwtIncompatible("java.io.ObjectInputStream") 90 private void readObject(ObjectInputStream stream) 91 throws IOException, ClassNotFoundException { 92 stream.defaultReadObject(); 93 int distinctElements = Serialization.readCount(stream); 94 setBackingMap( 95 Maps.<E, Count>newHashMapWithExpectedSize(distinctElements)); 96 Serialization.populateMultiset(this, stream, distinctElements); 97 } 98 99 @GwtIncompatible("Not needed in emulated source.") 100 private static final long serialVersionUID = 0; 101} 102