    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    }