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     * <p>See the Guava User Guide article on <a href=
032     * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multiset">
033     * {@code Multiset}</a>.
034     *
035     * @author Jared Levy
036     * @since 2.0 (imported from Google Collections Library)
037     */
038    @GwtCompatible(emulated = true)
039    public final class EnumMultiset<E extends Enum<E>> extends AbstractMapBasedMultiset<E> {
040      /** Creates an empty {@code EnumMultiset}. */
041      public static <E extends Enum<E>> EnumMultiset<E> create(Class<E> type) {
042        return new EnumMultiset<E>(type);
043      }
044    
045      /**
046       * Creates a new {@code EnumMultiset} containing the specified elements.
047       *
048       * <p>This implementation is highly efficient when {@code elements} is itself a {@link
049       * Multiset}.
050       *
051       * @param elements the elements that the multiset should contain
052       * @throws IllegalArgumentException if {@code elements} is empty
053       */
054      public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements) {
055        Iterator<E> iterator = elements.iterator();
056        checkArgument(iterator.hasNext(), "EnumMultiset constructor passed empty Iterable");
057        EnumMultiset<E> multiset = new EnumMultiset<E>(iterator.next().getDeclaringClass());
058        Iterables.addAll(multiset, elements);
059        return multiset;
060      }
061    
062      private transient Class<E> type;
063    
064      /** Creates an empty {@code EnumMultiset}. */
065      private EnumMultiset(Class<E> type) {
066        super(WellBehavedMap.wrap(new EnumMap<E, Count>(type)));
067        this.type = type;
068      }
069    
070      @GwtIncompatible("java.io.ObjectOutputStream")
071      private void writeObject(ObjectOutputStream stream) throws IOException {
072        stream.defaultWriteObject();
073        stream.writeObject(type);
074        Serialization.writeMultiset(this, stream);
075      }
076    
077      /**
078       * @serialData the {@code Class<E>} for the enum type, the number of distinct
079       *             elements, the first element, its count, the second element, its
080       *             count, and so on
081       */
082      @GwtIncompatible("java.io.ObjectInputStream")
083      private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
084        stream.defaultReadObject();
085        @SuppressWarnings("unchecked") // reading data stored by writeObject
086        Class<E> localType = (Class<E>) stream.readObject();
087        type = localType;
088        setBackingMap(WellBehavedMap.wrap(new EnumMap<E, Count>(type)));
089        Serialization.populateMultiset(this, stream);
090      }
091    
092      @GwtIncompatible("Not needed in emulated source")
093      private static final long serialVersionUID = 0;
094    }