MultiMap.java

  1. /*
  2.  * *********************************************************************************************************************
  3.  *
  4.  * TheseFoolishThings: Miscellaneous utilities
  5.  * http://tidalwave.it/projects/thesefoolishthings
  6.  *
  7.  * Copyright (C) 2009 - 2023 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
  12.  * the License. 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
  17.  * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the License for the
  18.  * specific language governing permissions and limitations under the License.
  19.  *
  20.  * *********************************************************************************************************************
  21.  *
  22.  * git clone https://bitbucket.org/tidalwave/thesefoolishthings-src
  23.  * git clone https://github.com/tidalwave-it/thesefoolishthings-src
  24.  *
  25.  * *********************************************************************************************************************
  26.  */
  27. package it.tidalwave.role.impl;

  28. import javax.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.  * @author  Fabrizio Giudici
  37.  *
  38.  **********************************************************************************************************************/
  39. public class MultiMap<K, V> extends HashMap<K, Set<V>>
  40.   {
  41.     private static final long serialVersionUID = 8834342771135005212L;

  42.     public synchronized void add (@Nonnull final K key, @Nonnull final V value)
  43.       {
  44.         internalGetValues(key).add(value);
  45.       }

  46.     public synchronized void addAll (@Nonnull final K key, @Nonnull final Collection<? extends V> values)
  47.       {
  48.         if (!values.isEmpty())
  49.           {
  50.             internalGetValues(key).addAll(values);
  51.           }
  52.       }

  53.     @Nonnull
  54.     public synchronized Set<V> getValues (@Nonnull final K key)
  55.       {
  56.         final var values = get(key);
  57.         return (values == null) ? Collections.emptySet() : Collections.unmodifiableSet(values);
  58.       }

  59.     @Nonnull
  60.     private Set<V> internalGetValues (@Nonnull final K key)
  61.       {
  62.         var values = get(key);

  63.         if (values == null)
  64.           {
  65.             values = new HashSet<>();
  66.             put(key, values);
  67.           }

  68.         return values;
  69.       }
  70.   }