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001    /*
002     * Copyright (C) 2007 The Guava Authors
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License");
005     * you may not use this file except in compliance with the License.
006     * You may obtain a copy of the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS,
012     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013     * See the License for the specific language governing permissions and
014     * limitations under the License.
015     */
016    
017    package com.google.common.collect;
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.LinkedHashMap;
026    
027    /**
028     * A {@code Multiset} implementation with predictable iteration order. Its
029     * iterator orders elements according to when the first occurrence of the
030     * element was added. When the multiset contains multiple instances of an
031     * element, those instances are consecutive in the iteration order. If all
032     * occurrences of an element are removed, after which that element is added to
033     * the multiset, the element will appear at the end of the iteration.
034     *
035     * @author Kevin Bourrillion
036     * @author Jared Levy
037     * @since 2.0 (imported from Google Collections Library)
038     */
039    @GwtCompatible(serializable = true, emulated = true)
040    @SuppressWarnings("serial") // we're overriding default serialization
041    public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> {
042    
043      /**
044       * Creates a new, empty {@code LinkedHashMultiset} using the default initial
045       * capacity.
046       */
047      public static <E> LinkedHashMultiset<E> create() {
048        return new LinkedHashMultiset<E>();
049      }
050    
051      /**
052       * Creates a new, empty {@code LinkedHashMultiset} with the specified expected
053       * number of distinct elements.
054       *
055       * @param distinctElements the expected number of distinct elements
056       * @throws IllegalArgumentException if {@code distinctElements} is negative
057       */
058      public static <E> LinkedHashMultiset<E> create(int distinctElements) {
059        return new LinkedHashMultiset<E>(distinctElements);
060      }
061    
062      /**
063       * Creates a new {@code LinkedHashMultiset} containing the specified elements.
064       *
065       * <p>This implementation is highly efficient when {@code elements} is itself
066       * a {@link Multiset}.
067       *
068       * @param elements the elements that the multiset should contain
069       */
070      public static <E> LinkedHashMultiset<E> create(
071          Iterable<? extends E> elements) {
072        LinkedHashMultiset<E> multiset =
073            create(Multisets.inferDistinctElements(elements));
074        Iterables.addAll(multiset, elements);
075        return multiset;
076      }
077    
078      private LinkedHashMultiset() {
079        super(new LinkedHashMap<E, Count>());
080      }
081    
082      private LinkedHashMultiset(int distinctElements) {
083        // Could use newLinkedHashMapWithExpectedSize() if it existed
084        super(new LinkedHashMap<E, Count>(Maps.capacity(distinctElements)));
085      }
086    
087      /**
088       * @serialData the number of distinct elements, the first element, its count,
089       *     the second element, its count, and so on
090       */
091      @GwtIncompatible("java.io.ObjectOutputStream")
092      private void writeObject(ObjectOutputStream stream) throws IOException {
093        stream.defaultWriteObject();
094        Serialization.writeMultiset(this, stream);
095      }
096    
097      @GwtIncompatible("java.io.ObjectInputStream")
098      private void readObject(ObjectInputStream stream)
099          throws IOException, ClassNotFoundException {
100        stream.defaultReadObject();
101        int distinctElements = Serialization.readCount(stream);
102        setBackingMap(new LinkedHashMap<E, Count>(
103            Maps.capacity(distinctElements)));
104        Serialization.populateMultiset(this, stream, distinctElements);
105      }
106    
107      @GwtIncompatible("not needed in emulated source")
108      private static final long serialVersionUID = 0;
109    }