/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.tinkerpop.gremlin.util.tools;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;
/**
* A number of static methods to interact with a multi map, i.e. a map that maps keys to sets of values.
*
* @author Matthias Broecheler (me@matthiasb.com)
*/
public final class MultiMap {
private MultiMap() {}
public static <K, V> boolean putAll(final Map<K, Set<V>> map, final K key, final Collection<V> values) {
return getMapSet(map, key).addAll(values);
}
public static <K, V> boolean put(final Map<K, Set<V>> map, final K key, final V value) {
return getMapSet(map, key).add(value);
}
public static <K, V> boolean containsEntry(final Map<K, Set<V>> map, final K key, final V value) {
final Set<V> set = map.get(key);
return set != null && set.contains(value);
}
public static <K, V> Set<V> get(final Map<K, Set<V>> map, final K key) {
final Set<V> set = getMapSet(map, key);
return set == null ? Collections.emptySet() : set;
}
private static <K, V> Set<V> getMapSet(final Map<K, Set<V>> map, final K key) {
Set<V> set = map.get(key);
if (set == null) {
set = new LinkedHashSet<>();
map.put(key, set);
}
return set;
}
}