1 /*
2 * *************************************************************************************************************************************************************
3 *
4 * TheseFoolishThings: Miscellaneous utilities
5 * http://tidalwave.it/projects/thesefoolishthings
6 *
7 * Copyright (C) 2009 - 2025 by Tidalwave s.a.s. (http://tidalwave.it)
8 *
9 * *************************************************************************************************************************************************************
10 *
11 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
12 * You may obtain a copy of the License at
13 *
14 * http://www.apache.org/licenses/LICENSE-2.0
15 *
16 * 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
17 * CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
18 *
19 * *************************************************************************************************************************************************************
20 *
21 * git clone https://bitbucket.org/tidalwave/thesefoolishthings-src
22 * git clone https://github.com/tidalwave-it/thesefoolishthings-src
23 *
24 * *************************************************************************************************************************************************************
25 */
26 package it.tidalwave.role.impl;
27
28 import jakarta.annotation.Nonnull;
29 import java.util.Collection;
30 import java.util.Collections;
31 import java.util.HashMap;
32 import java.util.HashSet;
33 import java.util.Set;
34
35 /***************************************************************************************************************************************************************
36 *
37 * @author Fabrizio Giudici
38 *
39 **************************************************************************************************************************************************************/
40 public class MultiMap<K, V> extends HashMap<K, Set<V>>
41 {
42 private static final long serialVersionUID = 8834342771135005212L;
43
44 public synchronized void add (@Nonnull final K key, @Nonnull final V value)
45 {
46 internalGetValues(key).add(value);
47 }
48
49 public synchronized void addAll (@Nonnull final K key, @Nonnull final Collection<? extends V> values)
50 {
51 if (!values.isEmpty())
52 {
53 internalGetValues(key).addAll(values);
54 }
55 }
56
57 @Nonnull
58 public synchronized Set<V> getValues (@Nonnull final K key)
59 {
60 final var values = get(key);
61 return (values == null) ? Collections.emptySet() : Collections.unmodifiableSet(values);
62 }
63
64 @Nonnull
65 private Set<V> internalGetValues (@Nonnull final K key)
66 {
67 var values = get(key);
68
69 if (values == null)
70 {
71 values = new HashSet<>();
72 put(key, values);
73 }
74
75 return values;
76 }
77 }