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001    /*
002     * Copyright (C) 2007 The Guava Authors
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
005     * in compliance with the License. You may obtain a copy of the License at
006     *
007     * http://www.apache.org/licenses/LICENSE-2.0
008     *
009     * Unless required by applicable law or agreed to in writing, software distributed under the License
010     * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
011     * or implied. See the License for the specific language governing permissions and limitations under
012     * the License.
013     */
014    
015    package com.google.common.collect;
016    
017    import static com.google.common.base.Preconditions.checkArgument;
018    
019    import com.google.common.annotations.GwtCompatible;
020    import com.google.common.annotations.GwtIncompatible;
021    
022    import java.io.IOException;
023    import java.io.ObjectInputStream;
024    import java.io.ObjectOutputStream;
025    import java.util.EnumMap;
026    import java.util.Iterator;
027    
028    /**
029     * Multiset implementation backed by an {@link EnumMap}.
030     *
031     * @author Jared Levy
032     * @since 2.0 (imported from Google Collections Library)
033     */
034    @GwtCompatible(emulated = true)
035    public final class EnumMultiset<E extends Enum<E>> extends AbstractMapBasedMultiset<E> {
036      /** Creates an empty {@code EnumMultiset}. */
037      public static <E extends Enum<E>> EnumMultiset<E> create(Class<E> type) {
038        return new EnumMultiset<E>(type);
039      }
040    
041      /**
042       * Creates a new {@code EnumMultiset} containing the specified elements.
043       *
044       * <p>This implementation is highly efficient when {@code elements} is itself a {@link
045       * Multiset}.
046       *
047       * @param elements the elements that the multiset should contain
048       * @throws IllegalArgumentException if {@code elements} is empty
049       */
050      public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements) {
051        Iterator<E> iterator = elements.iterator();
052        checkArgument(iterator.hasNext(), "EnumMultiset constructor passed empty Iterable");
053        EnumMultiset<E> multiset = new EnumMultiset<E>(iterator.next().getDeclaringClass());
054        Iterables.addAll(multiset, elements);
055        return multiset;
056      }
057    
058      private transient Class<E> type;
059    
060      /** Creates an empty {@code EnumMultiset}. */
061      private EnumMultiset(Class<E> type) {
062        super(WellBehavedMap.wrap(new EnumMap<E, Count>(type)));
063        this.type = type;
064      }
065    
066      @GwtIncompatible("java.io.ObjectOutputStream")
067      private void writeObject(ObjectOutputStream stream) throws IOException {
068        stream.defaultWriteObject();
069        stream.writeObject(type);
070        Serialization.writeMultiset(this, stream);
071      }
072    
073      /**
074       * @serialData the {@code Class<E>} for the enum type, the number of distinct
075       *             elements, the first element, its count, the second element, its
076       *             count, and so on
077       */
078      @GwtIncompatible("java.io.ObjectInputStream")
079      private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
080        stream.defaultReadObject();
081        @SuppressWarnings("unchecked") // reading data stored by writeObject
082        Class<E> localType = (Class<E>) stream.readObject();
083        type = localType;
084        setBackingMap(WellBehavedMap.wrap(new EnumMap<E, Count>(type)));
085        Serialization.populateMultiset(this, stream);
086      }
087    
088      @GwtIncompatible("Not needed in emulated source")
089      private static final long serialVersionUID = 0;
090    }