1 /* 2 * Copyright (C) 2007 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 5 * in compliance with the License. You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software distributed under the License 10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 11 * or implied. See the License for the specific language governing permissions and limitations under 12 * the License. 13 */ 14 15 package com.google.common.collect; 16 17 import static com.google.common.base.Preconditions.checkArgument; 18 19 import com.google.common.annotations.GwtCompatible; 20 21 import java.util.EnumMap; 22 import java.util.Iterator; 23 24 /** 25 * Multiset implementation backed by an {@link EnumMap}. 26 * 27 * <p>See the Guava User Guide article on <a href= 28 * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multiset"> 29 * {@code Multiset}</a>. 30 * 31 * @author Jared Levy 32 * @since 2.0 (imported from Google Collections Library) 33 */ 34 @GwtCompatible(emulated = true) 35 public final class EnumMultiset<E extends Enum<E>> extends AbstractMapBasedMultiset<E> { 36 /** Creates an empty {@code EnumMultiset}. */ 37 public static <E extends Enum<E>> EnumMultiset<E> create(Class<E> type) { 38 return new EnumMultiset<E>(type); 39 } 40 41 /** 42 * Creates a new {@code EnumMultiset} containing the specified elements. 43 * 44 * <p>This implementation is highly efficient when {@code elements} is itself a {@link 45 * Multiset}. 46 * 47 * @param elements the elements that the multiset should contain 48 * @throws IllegalArgumentException if {@code elements} is empty 49 */ 50 public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements) { 51 Iterator<E> iterator = elements.iterator(); 52 checkArgument(iterator.hasNext(), "EnumMultiset constructor passed empty Iterable"); 53 EnumMultiset<E> multiset = new EnumMultiset<E>(iterator.next().getDeclaringClass()); 54 Iterables.addAll(multiset, elements); 55 return multiset; 56 } 57 58 /** 59 * Returns a new {@code EnumMultiset} instance containing the given elements. Unlike 60 * {@link EnumMultiset#create(Iterable)}, this method does not produce an exception on an empty 61 * iterable. 62 * 63 * @since 14.0 64 */ 65 public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements, Class<E> type) { 66 EnumMultiset<E> result = create(type); 67 Iterables.addAll(result, elements); 68 return result; 69 } 70 71 private transient Class<E> type; 72 73 /** Creates an empty {@code EnumMultiset}. */ 74 private EnumMultiset(Class<E> type) { 75 super(WellBehavedMap.wrap(new EnumMap<E, Count>(type))); 76 this.type = type; 77 } 78 } 79 80
