import org.jspecify.annotations.Nullable;

/** Collectors utilities for {@code common.collect} internals. */
@GwtCompatible
@IgnoreJRERequirement // used only from APIs with Java 8 types in them
final class CollectCollectors {

  private static final Collector<Object, ?, ImmutableList<Object>> TO_IMMUTABLE_LIST =
      Collector.of(
          ImmutableList::builder,
          ImmutableList.Builder::add,

import java.util.stream.Collector;
import java.util.stream.Stream;
import org.jspecify.annotations.Nullable;

/** Collectors utilities for {@code common.collect} internals. */
@GwtCompatible
final class CollectCollectors {

  private static final Collector<Object, ?, ImmutableList<Object>> TO_IMMUTABLE_LIST =
      Collector.of(
          ImmutableList::builder,
          ImmutableList.Builder::add,

      Collector<T, ?, ImmutableSortedMap<K, V>> toImmutableSortedMap(
          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    return CollectCollectors.toImmutableSortedMap(Ordering.natural(), keyFunction, valueFunction);
  }

  public static <T extends @Nullable Object, K, V>
      Collector<T, ?, ImmutableSortedMap<K, V>> toImmutableSortedMap(

          java.util.function.Function<? super T, ? extends K> keyFunction,
          java.util.function.Function<? super T, ? extends V> valueFunction,
          java.util.function.Supplier<M> multimapSupplier) {
    return CollectCollectors.<T, K, V, M>toMultimap(keyFunction, valueFunction, multimapSupplier);
  }

  /**
   * Returns a {@code Collector} accumulating entries into a {@code Multimap} generated from the

          java.util.function.Function<? super T, ? extends K> keyFunction,
          java.util.function.Function<? super T, ? extends V> valueFunction,
          java.util.function.Supplier<M> multimapSupplier) {
    return CollectCollectors.<T, K, V, M>toMultimap(keyFunction, valueFunction, multimapSupplier);
  }

  /**
   * Returns a {@code Collector} accumulating entries into a {@code Multimap} generated from the

   * encounter order.
   *
   * @since 21.0
   */
  public static <E> Collector<E, ?, ImmutableMultiset<E>> toImmutableMultiset() {
    return CollectCollectors.toImmutableMultiset(Function.identity(), e -> 1);
  }

  /**
   * Returns a {@code Collector} that accumulates elements into an {@code ImmutableMultiset} whose

      Collector<T, ?, ImmutableBiMap<K, V>> toImmutableBiMap(
          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    return CollectCollectors.toImmutableBiMap(keyFunction, valueFunction);
  }

  // Casting to any type is safe because the set will never hold any elements.
  @SuppressWarnings("unchecked")
  public static <K, V> ImmutableBiMap<K, V> of() {

public abstract class ImmutableSet<E> extends ImmutableCollection<E> implements Set<E> {
  ImmutableSet() {}

  public static <E> Collector<E, ?, ImmutableSet<E>> toImmutableSet() {
    return CollectCollectors.toImmutableSet();
  }

  // Casting to any type is safe because the set will never hold any elements.
  @SuppressWarnings({"unchecked"})
  public static <E> ImmutableSet<E> of() {

   */
  @IgnoreJRERequirement // Users will use this only if they're already using streams.
  public static <E> Collector<E, ?, ImmutableMultiset<E>> toImmutableMultiset() {
    return CollectCollectors.toImmutableMultiset(Function.identity(), e -> 1);
  }

  /**
   * Returns a {@code Collector} that accumulates elements into an {@code ImmutableMultiset} whose

      Collector<T, ?, ImmutableListMultimap<K, V>> toImmutableListMultimap(
          Function<? super T, ? extends K> keyFunction,
          Function<? super T, ? extends V> valueFunction) {
    return CollectCollectors.toImmutableListMultimap(keyFunction, valueFunction);
  }

  /**
   * Returns a {@code Collector} accumulating entries into an {@code ImmutableListMultimap}. Each