    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}