    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     * <p>See the Guava User Guide article on <a href=
    036     * "http://code.google.com/p/guava-libraries/wiki/NewCollectionTypesExplained#Multiset">
    037     * {@code Multiset}</a>.
    038     *
    039     * @author Kevin Bourrillion
    040     * @author Jared Levy
    041     * @since 2.0 (imported from Google Collections Library)
    042     */
    043    @GwtCompatible(serializable = true, emulated = true)
    044    @SuppressWarnings("serial") // we're overriding default serialization
    045    public final class LinkedHashMultiset<E> extends AbstractMapBasedMultiset<E> {
    046
    047      /**
    048       * Creates a new, empty {@code LinkedHashMultiset} using the default initial
    049       * capacity.
    050       */
    051      public static <E> LinkedHashMultiset<E> create() {
    052        return new LinkedHashMultiset<E>();
    053      }
    054
    055      /**
    056       * Creates a new, empty {@code LinkedHashMultiset} with the specified expected
    057       * number of distinct elements.
    058       *
    059       * @param distinctElements the expected number of distinct elements
    060       * @throws IllegalArgumentException if {@code distinctElements} is negative
    061       */
    062      public static <E> LinkedHashMultiset<E> create(int distinctElements) {
    063        return new LinkedHashMultiset<E>(distinctElements);
    064      }
    065
    066      /**
    067       * Creates a new {@code LinkedHashMultiset} containing the specified elements.
    068       *
    069       * <p>This implementation is highly efficient when {@code elements} is itself
    070       * a {@link Multiset}.
    071       *
    072       * @param elements the elements that the multiset should contain
    073       */
    074      public static <E> LinkedHashMultiset<E> create(
    075          Iterable<? extends E> elements) {
    076        LinkedHashMultiset<E> multiset =
    077            create(Multisets.inferDistinctElements(elements));
    078        Iterables.addAll(multiset, elements);
    079        return multiset;
    080      }
    081
    082      private LinkedHashMultiset() {
    083        super(new LinkedHashMap<E, Count>());
    084      }
    085
    086      private LinkedHashMultiset(int distinctElements) {
    087        // Could use newLinkedHashMapWithExpectedSize() if it existed
    088        super(new LinkedHashMap<E, Count>(Maps.capacity(distinctElements)));
    089      }
    090
    091      /**
    092       * @serialData the number of distinct elements, the first element, its count,
    093       *     the second element, its count, and so on
    094       */
    095      @GwtIncompatible("java.io.ObjectOutputStream")
    096      private void writeObject(ObjectOutputStream stream) throws IOException {
    097        stream.defaultWriteObject();
    098        Serialization.writeMultiset(this, stream);
    099      }
    100
    101      @GwtIncompatible("java.io.ObjectInputStream")
    102      private void readObject(ObjectInputStream stream)
    103          throws IOException, ClassNotFoundException {
    104        stream.defaultReadObject();
    105        int distinctElements = Serialization.readCount(stream);
    106        setBackingMap(new LinkedHashMap<E, Count>(
    107            Maps.capacity(distinctElements)));
    108        Serialization.populateMultiset(this, stream, distinctElements);
    109      }
    110
    111      @GwtIncompatible("not needed in emulated source")
    112      private static final long serialVersionUID = 0;
    113    }