ArrayListCollectorSupport.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.util.spi;

  28. import javax.annotation.Nonnull;
  29. import java.util.ArrayList;
  30. import java.util.Collections;
  31. import java.util.List;
  32. import java.util.Set;
  33. import java.util.function.BiConsumer;
  34. import java.util.function.BinaryOperator;
  35. import java.util.function.Supplier;
  36. import java.util.stream.Collector;

  37. /***********************************************************************************************************************
  38.  *
  39.  * A support {@link Collector} which uses an {@link ArrayList} as the accumulator.
  40.  *
  41.  * @param  <COLLECTED_TYPE>     the type of collected items
  42.  * @param  <COLLECTING_TYPE>    the type of collecting item
  43.  *
  44.  * @author  Fabrizio Giudici
  45.  *
  46.  **********************************************************************************************************************/
  47. public abstract class ArrayListCollectorSupport<COLLECTED_TYPE, COLLECTING_TYPE>
  48.         implements Collector<COLLECTED_TYPE, List<COLLECTED_TYPE>, COLLECTING_TYPE>
  49.   {
  50.     @Override @Nonnull
  51.     public Supplier<List<COLLECTED_TYPE>> supplier()
  52.       {
  53.         return ArrayList::new;
  54.       }

  55.     @Override @Nonnull
  56.     public BiConsumer<List<COLLECTED_TYPE>, COLLECTED_TYPE> accumulator()
  57.       {
  58.         return List::add;
  59.       }

  60.     @Override @Nonnull
  61.     public BinaryOperator<List<COLLECTED_TYPE>> combiner()
  62.       {
  63.         return (left, right) -> { left.addAll(right); return left; };
  64.       }

  65.     @Override @Nonnull
  66.     public Set<Characteristics> characteristics()
  67.       {
  68.         // Not CONCURRENT since ArrayList is not thread-safe
  69.         return Collections.emptySet();
  70.       }
  71.   }