    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 * </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     * Constructor needed for subclass serialisation.
    043     */
    044    protected AbstractSetValuedMap() {
    045        super();
    046    }
    047
    048    /**
    049     * A constructor that wraps, not copies
    050     *
    051     * @param map  the map to wrap, must not be null
    052     * @throws NullPointerException if the map is null
    053     */
    054    protected AbstractSetValuedMap(final Map<K, ? extends Set<V>> map) {
    055        super(map);
    056    }
    057
    058    // -----------------------------------------------------------------------
    059    @Override
    060    @SuppressWarnings("unchecked")
    061    protected Map<K, Set<V>> getMap() {
    062        return (Map<K, Set<V>>) super.getMap();
    063    }
    064
    065    /**
    066     * Creates a new value collection using the provided factory.
    067     * @return a new list
    068     */
    069    @Override
    070    protected abstract Set<V> createCollection();
    071
    072    // -----------------------------------------------------------------------
    073    /**
    074     * Gets the set of values associated with the specified key. This would
    075     * return an empty set in case the mapping is not present
    076     *
    077     * @param key  the key to retrieve
    078     * @return the <code>Set</code> of values, will return an empty
    079     *   <code>Set</code> for no mapping
    080     */
    081    @Override
    082    public Set<V> get(final K key) {
    083        return wrappedCollection(key);
    084    }
    085
    086    @Override
    087    Set<V> wrappedCollection(final K key) {
    088        return new WrappedSet(key);
    089    }
    090
    091    /**
    092     * Removes all values associated with the specified key.
    093     * <p>
    094     * A subsequent <code>get(Object)</code> would return an empty set.
    095     *
    096     * @param key the key to remove values from
    097     * @return the <code>Set</code> of values removed, will return an empty,
    098     *   unmodifiable set for no mapping found.
    099     */
    100    @Override
    101    public Set<V> remove(final Object key) {
    102        return SetUtils.emptyIfNull(getMap().remove(key));
    103    }
    104
    105    // -----------------------------------------------------------------------
    106    /**
    107     * Wrapped set to handle add and remove on the collection returned by
    108     * {@code get(Object)}.
    109     */
    110    private class WrappedSet extends WrappedCollection implements Set<V> {
    111
    112        public WrappedSet(final K key) {
    113            super(key);
    114        }
    115
    116        @Override
    117        public boolean equals(final Object other) {
    118            final Set<V> set = (Set<V>) getMapping();
    119            if (set == null) {
    120                return Collections.emptySet().equals(other);
    121            }
    122            if (!(other instanceof Set)) {
    123                return false;
    124            }
    125            final Set<?> otherSet = (Set<?>) other;
    126            return SetUtils.isEqualSet(set, otherSet);
    127        }
    128
    129        @Override
    130        public int hashCode() {
    131            final Set<V> set = (Set<V>) getMapping();
    132            return SetUtils.hashCodeForSet(set);
    133        }
    134
    135    }
    136
    137}