    001/*
    002 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
    003 *
    004 * Project and contact information: http://www.cascading.org/
    005 *
    006 * This file is part of the Cascading project.
    007 *
    008 * Licensed under the Apache License, Version 2.0 (the "License");
    009 * you may not use this file except in compliance with the License.
    010 * You may obtain a copy of the License at
    011 *
    012 *     http://www.apache.org/licenses/LICENSE-2.0
    013 *
    014 * Unless required by applicable law or agreed to in writing, software
    015 * distributed under the License is distributed on an "AS IS" BASIS,
    016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    017 * See the License for the specific language governing permissions and
    018 * limitations under the License.
    019 */
    020
    021package cascading.util;
    022
    023import java.util.Collections;
    024import java.util.HashMap;
    025import java.util.LinkedHashSet;
    026import java.util.Map;
    027import java.util.Set;
    028
    029/**
    030 *
    031 */
    032public class SetMultiMap<K, V> extends MultiMap<Set<V>, K, V>
    033  {
    034  @Override
    035  protected Map<K, Set<V>> createMap()
    036    {
    037    return new HashMap<>();
    038    }
    039
    040  protected Set<V> createCollection()
    041    {
    042    return new LinkedHashSet<>();
    043    }
    044
    045  protected Set<V> emptyCollection()
    046    {
    047    return Collections.emptySet();
    048    }
    049  }