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 import org.checkerframework.checker.nullness.qual.Nullable; 22 23 /** 24 * Multiset implementation that uses hashing for key and entry access. 25 * 26 * @author Kevin Bourrillion 27 * @author Jared Levy 28 * @since 2.0 29 */ 30 @GwtCompatible(serializable = true, emulated = true) 31 @ElementTypesAreNonnullByDefault 32 public final class HashMultiset<E extends @Nullable Object> extends AbstractMapBasedMultiset<E> { 33 34 /** Creates a new, empty {@code HashMultiset} using the default initial capacity. */ create()35 public static <E extends @Nullable Object> HashMultiset<E> create() { 36 return create(ObjectCountHashMap.DEFAULT_SIZE); 37 } 38 39 /** 40 * Creates a new, empty {@code HashMultiset} with the specified expected number of distinct 41 * elements. 42 * 43 * @param distinctElements the expected number of distinct elements 44 * @throws IllegalArgumentException if {@code distinctElements} is negative 45 */ create(int distinctElements)46 public static <E extends @Nullable Object> HashMultiset<E> create(int distinctElements) { 47 return new HashMultiset<E>(distinctElements); 48 } 49 50 /** 51 * Creates a new {@code HashMultiset} containing the specified elements. 52 * 53 * <p>This implementation is highly efficient when {@code elements} is itself a {@link Multiset}. 54 * 55 * @param elements the elements that the multiset should contain 56 */ create( Iterable<? extends E> elements)57 public static <E extends @Nullable Object> HashMultiset<E> create( 58 Iterable<? extends E> elements) { 59 HashMultiset<E> multiset = create(Multisets.inferDistinctElements(elements)); 60 Iterables.addAll(multiset, elements); 61 return multiset; 62 } 63 HashMultiset(int distinctElements)64 HashMultiset(int distinctElements) { 65 super(distinctElements); 66 } 67 68 @Override newBackingMap(int distinctElements)69 ObjectCountHashMap<E> newBackingMap(int distinctElements) { 70 return new ObjectCountHashMap<>(distinctElements); 71 } 72 73 @GwtIncompatible // Not needed in emulated source. 74 private static final long serialVersionUID = 0; 75 } 76