001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      https://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.commons.collections4.multimap;
018
019import java.util.Collections;
020import java.util.Map;
021import java.util.Set;
022
023import org.apache.commons.collections4.SetUtils;
024import org.apache.commons.collections4.SetValuedMap;
025
026/**
027 * Abstract implementation of the {@link SetValuedMap} interface to simplify the
028 * creation of subclass implementations.
029 * <p>
030 * Subclasses specify a Map implementation to use as the internal storage and
031 * the Set implementation to use as values.
032 * </p>
033 *
034 * @param <K> The type of the keys in this map
035 * @param <V> The type of the values in this map
036 * @since 4.1
037 */
038public abstract class AbstractSetValuedMap<K, V> extends AbstractMultiValuedMap<K, V>
039    implements SetValuedMap<K, V> {
040
041    /**
042     * Wrapped set to handle add and remove on the collection returned by
043     * {@code get(Object)}.
044     */
045    private final class WrappedSet extends WrappedCollection implements Set<V> {
046
047        WrappedSet(final K key) {
048            super(key);
049        }
050
051        @Override
052        public boolean equals(final Object other) {
053            final Set<V> set = (Set<V>) getMapping();
054            if (set == null) {
055                return Collections.emptySet().equals(other);
056            }
057            if (!(other instanceof Set)) {
058                return false;
059            }
060            final Set<?> otherSet = (Set<?>) other;
061            return SetUtils.isEqualSet(set, otherSet);
062        }
063
064        @Override
065        public int hashCode() {
066            final Set<V> set = (Set<V>) getMapping();
067            return SetUtils.hashCodeForSet(set);
068        }
069
070    }
071
072    /**
073     * Constructor needed for subclass serialization.
074     */
075    protected AbstractSetValuedMap() {
076    }
077
078    /**
079     * A constructor that wraps, not copies
080     *
081     * @param map  The map to wrap, must not be null
082     * @throws NullPointerException if the map is null
083     */
084    protected AbstractSetValuedMap(final Map<K, ? extends Set<V>> map) {
085        super(map);
086    }
087
088    /**
089     * Creates a new value collection using the provided factory.
090     *
091     * @return A new set
092     */
093    @Override
094    protected abstract Set<V> createCollection();
095
096    /**
097     * Gets the set of values associated with the specified key. This would
098     * return an empty set in case the mapping is not present
099     *
100     * @param key  The key to retrieve
101     * @return The {@code Set} of values, will return an empty
102     *   {@code Set} for no mapping
103     */
104    @Override
105    public Set<V> get(final K key) {
106        return wrappedCollection(key);
107    }
108
109    @Override
110    @SuppressWarnings("unchecked")
111    protected Map<K, Set<V>> getMap() {
112        return (Map<K, Set<V>>) super.getMap();
113    }
114
115    /**
116     * Removes all values associated with the specified key.
117     * <p>
118     * A subsequent {@code get(Object)} would return an empty set.
119     * </p>
120     *
121     * @param key The key to remove values from
122     * @return The {@code Set} of values removed, will return an empty,
123     *   unmodifiable set for no mapping found.
124     */
125    @Override
126    public Set<V> remove(final Object key) {
127        return SetUtils.emptyIfNull(getMap().remove(key));
128    }
129
130    @Override
131    Set<V> wrappedCollection(final K key) {
132        return new WrappedSet(key);
133    }
134}