guava/src/com/google/common/collect/AbstractSortedSetMultimap.java

/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;

import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Map;
import java.util.SortedSet;

import javax.annotation.Nullable;

/**
 * Basic implementation of the {@link SortedSetMultimap} interface. It's a
 * wrapper around {@link AbstractMapBasedMultimap} that converts the returned
 * collections into sorted sets. The {@link #createCollection} method
 * must return a {@code SortedSet}.
 *
 * @author Jared Levy
 */
@GwtCompatible
abstract class AbstractSortedSetMultimap<K, V>
    extends AbstractSetMultimap<K, V> implements SortedSetMultimap<K, V> {
  /**
   * Creates a new multimap that uses the provided map.
   *
   * @param map place to store the mapping from each key to its corresponding
   *     values
   */
  protected AbstractSortedSetMultimap(Map<K, Collection<V>> map) {
    super(map);
  }

  @Override
  abstract SortedSet<V> createCollection();

  @Override
  SortedSet<V> createUnmodifiableEmptyCollection() {
    Comparator<? super V> comparator = valueComparator();
    if (comparator == null) {
      return Collections.unmodifiableSortedSet(createCollection());
    } else {
      return ImmutableSortedSet.emptySet(valueComparator());
    }
  }

  // Following Javadoc copied from Multimap and SortedSetMultimap.

  /**
   * Returns a collection view of all values associated with a key. If no
   * mappings in the multimap have the provided key, an empty collection is
   * returned.
   *
   * <p>Changes to the returned collection will update the underlying multimap,
   * and vice versa.
   *
   * <p>Because a {@code SortedSetMultimap} has unique sorted values for a given
   * key, this method returns a {@link SortedSet}, instead of the
   * {@link Collection} specified in the {@link Multimap} interface.
   */
  @Override public SortedSet<V> get(@Nullable K key) {
    return (SortedSet<V>) super.get(key);
  }

  /**
   * Removes all values associated with a given key. The returned collection is
   * immutable.
   *
   * <p>Because a {@code SortedSetMultimap} has unique sorted values for a given
   * key, this method returns a {@link SortedSet}, instead of the
   * {@link Collection} specified in the {@link Multimap} interface.
   */
  @Override public SortedSet<V> removeAll(@Nullable Object key) {
    return (SortedSet<V>) super.removeAll(key);
  }

  /**
   * Stores a collection of values with the same key, replacing any existing
   * values for that key. The returned collection is immutable.
   *
   * <p>Because a {@code SortedSetMultimap} has unique sorted values for a given
   * key, this method returns a {@link SortedSet}, instead of the
   * {@link Collection} specified in the {@link Multimap} interface.
   *
   * <p>Any duplicates in {@code values} will be stored in the multimap once.
   */
  @Override public SortedSet<V> replaceValues(
      @Nullable K key, Iterable<? extends V> values) {
    return (SortedSet<V>) super.replaceValues(key, values);
  }

  /**
   * Returns a map view that associates each key with the corresponding values
   * in the multimap. Changes to the returned map, such as element removal, will
   * update the underlying multimap. The map does not support {@code setValue}
   * on its entries, {@code put}, or {@code putAll}.
   *
   * <p>When passed a key that is present in the map, {@code
   * asMap().get(Object)} has the same behavior as {@link #get}, returning a
   * live collection. When passed a key that is not present, however, {@code
   * asMap().get(Object)} returns {@code null} instead of an empty collection.
   *
   * <p>Though the method signature doesn't say so explicitly, the returned map
   * has {@link SortedSet} values.
   */
  @Override public Map<K, Collection<V>> asMap() {
    return super.asMap();
  }

  /**
   * {@inheritDoc}
   *
   * Consequently, the values do not follow their natural ordering or the
   * ordering of the value comparator.
   */
  @Override public Collection<V> values() {
    return super.values();
  }

  private static final long serialVersionUID = 430848587173315748L;
}