ArrayListCollectorSupport.java

  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.util.spi;

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

  36. /***************************************************************************************************************************************************************
  37.  *
  38.  * A support {@link Collector} which uses an {@link ArrayList} as the accumulator.
  39.  *
  40.  * @param  <COLLECTED_TYPE>     the type of collected items
  41.  * @param  <COLLECTING_TYPE>    the type of collecting item
  42.  *
  43.  * @author  Fabrizio Giudici
  44.  *
  45.  **************************************************************************************************************************************************************/
  46. public abstract class ArrayListCollectorSupport<COLLECTED_TYPE, COLLECTING_TYPE>
  47.         implements Collector<COLLECTED_TYPE, List<COLLECTED_TYPE>, COLLECTING_TYPE>
  48.   {
  49.     @Override @Nonnull
  50.     public Supplier<List<COLLECTED_TYPE>> supplier()
  51.       {
  52.         return ArrayList::new;
  53.       }

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

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

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