content: /*
   * 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.cassandra.utils;
  
  import java.util.Map;
  import java.util.SortedSet;
  import java.util.TreeSet;
  import java.util.function.Function;
  import java.util.stream.Collector;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.ImmutableMap;
  import com.google.common.collect.ImmutableSet;
  
  /**
   * Some extra Collector implementations.
   * <p>
   * Named Collectors3 just in case Guava ever makes a Collectors2
   */
  public class Collectors3
  {
      private static final Collector.Characteristics[] LIST_CHARACTERISTICS = new Collector.Characteristics[]{};
  
      public static <T> Collector<T, ?, ImmutableList<T>> toImmutableList()
      {
          return Collector.of(ImmutableList.Builder<T>::new,
                              ImmutableList.Builder<T>::add,
                              (l, r) -> l.addAll(r.build()),
                              ImmutableList.Builder<T>::build,
                              LIST_CHARACTERISTICS);
      }
  
      private static final Collector.Characteristics[] SET_CHARACTERISTICS = new Collector.Characteristics[]{ Collector.Characteristics.UNORDERED };
  
      private static final Collector.Characteristics[] SORTED_SET_CHARACTERISTICS = new Collector.Characteristics[]{ Collector.Characteristics.UNORDERED };
  
      public static <T> Collector<T, ?, ImmutableSet<T>> toImmutableSet()
      {
          return Collector.of(ImmutableSet.Builder<T>::new,
                              ImmutableSet.Builder<T>::add,
                              (l, r) -> l.addAll(r.build()),
                              ImmutableSet.Builder<T>::build,
                              SET_CHARACTERISTICS);
      }
  
      private static final Collector.Characteristics[] MAP_CHARACTERISTICS = new Collector.Characteristics[]{ Collector.Characteristics.UNORDERED };
  
      public static <K, V> Collector<Map.Entry<K, V>, ?, ImmutableMap<K, V>> toImmutableMap()
      {
          return Collector.of(ImmutableMap.Builder<K, V>::new,
                              ImmutableMap.Builder<K, V>::put,
                              (l, r) -> l.putAll(r.build()),
                              ImmutableMap.Builder<K, V>::build,
                              MAP_CHARACTERISTICS);
      }
  
      public static <T, K, V> Collector<T, ?, ImmutableMap<K, V>> toImmutableMap(Function<? super T, ? extends K> keyMapper, Function<? super T, ? extends V> valueMapper)
      {
          return Collector.of(ImmutableMap.Builder<K, V>::new,
                              (b, t) -> b.put(keyMapper.apply(t), valueMapper.apply(t)),
                              (l, r) -> l.putAll(r.build()),
                              ImmutableMap.Builder::build,
                              MAP_CHARACTERISTICS);
      }
  
      public static <T> Collector<T, SortedSet<T>, SortedSet<T>> toSortedSet()
      {
          return Collector.of(() -> new TreeSet<T>(),
                              (set, value) -> set.add(value),
                              (set1, set2) -> {
                                  set1.addAll(set2);
                                  return set1;
                              },
                              set -> set,
                              SORTED_SET_CHARACTERISTICS);
      }
  }
  