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 *      http://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 *
033 * @param <K> the type of the keys in this map
034 * @param <V> the type of the values in this map
035 * @since 4.1
036 */
037public abstract class AbstractSetValuedMap<K, V> extends AbstractMultiValuedMap<K, V>
038    implements SetValuedMap<K, V> {
039
040    /**
041     * Constructor needed for subclass serialisation.
042     */
043    protected AbstractSetValuedMap() {
044        super();
045    }
046
047    /**
048     * A constructor that wraps, not copies
049     *
050     * @param map  the map to wrap, must not be null
051     * @throws NullPointerException if the map is null
052     */
053    protected AbstractSetValuedMap(final Map<K, ? extends Set<V>> map) {
054        super(map);
055    }
056
057    // -----------------------------------------------------------------------
058    @Override
059    @SuppressWarnings("unchecked")
060    protected Map<K, Set<V>> getMap() {
061        return (Map<K, Set<V>>) super.getMap();
062    }
063
064    /**
065     * Creates a new value collection using the provided factory.
066     * @return a new list
067     */
068    @Override
069    protected abstract Set<V> createCollection();
070
071    // -----------------------------------------------------------------------
072    /**
073     * Gets the set of values associated with the specified key. This would
074     * return an empty set in case the mapping is not present
075     *
076     * @param key  the key to retrieve
077     * @return the <code>Set</code> of values, will return an empty
078     *   <code>Set</code> for no mapping
079     */
080    @Override
081    public Set<V> get(final K key) {
082        return wrappedCollection(key);
083    }
084
085    @Override
086    Set<V> wrappedCollection(final K key) {
087        return new WrappedSet(key);
088    }
089
090    /**
091     * Removes all values associated with the specified key.
092     * <p>
093     * A subsequent <code>get(Object)</code> would return an empty set.
094     *
095     * @param key the key to remove values from
096     * @return the <code>Set</code> of values removed, will return an empty,
097     *   unmodifiable set for no mapping found.
098     */
099    @Override
100    public Set<V> remove(final Object key) {
101        return SetUtils.emptyIfNull(getMap().remove(key));
102    }
103
104    // -----------------------------------------------------------------------
105    /**
106     * Wrapped set to handle add and remove on the collection returned by
107     * {@code get(Object)}.
108     */
109    private class WrappedSet extends WrappedCollection implements Set<V> {
110
111        public WrappedSet(final K key) {
112            super(key);
113        }
114
115        @Override
116        public boolean equals(final Object other) {
117            final Set<V> set = (Set<V>) getMapping();
118            if (set == null) {
119                return Collections.emptySet().equals(other);
120            }
121            if (!(other instanceof Set)) {
122                return false;
123            }
124            final Set<?> otherSet = (Set<?>) other;
125            return SetUtils.isEqualSet(set, otherSet);
126        }
127
128        @Override
129        public int hashCode() {
130            final Set<V> set = (Set<V>) getMapping();
131            return SetUtils.hashCodeForSet(set);
132        }
133
134    }
135
136}