import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeSet;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.atomic.AtomicInteger;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * A comparator, with additional methods to support common operations. This is an "enriched" version

  // (which is fortunate because Animal Sniffer doesn't look for @IgnoreJRERequirement on fields)
  static final int SPLITERATOR_CHARACTERISTICS =
      Spliterator.IMMUTABLE | Spliterator.NONNULL | Spliterator.ORDERED;

  ImmutableCollection() {}

  /** Returns an unmodifiable iterator across the elements in this collection. */
  @Override
  public abstract UnmodifiableIterator<E> iterator();

import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.PriorityQueue;
import java.util.Queue;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * This class contains static utility methods that operate on or return objects of type {@link

        String[] values = null;
        if (input instanceof String[]) {
            values = (String[]) input;
        } else if (input instanceof List) {
            values = ((List<?>) input).stream().filter(Objects::nonNull).map(Object::toString).toArray(n -> new String[n]);
        } else if (input instanceof String) {
            return input.toString();
        }
        if (values != null) {

     */
    public ImmutableSet<@NonNull E> immutableCopy() {
      // Not using ImmutableSet.copyOf() to avoid iterating thrice (isEmpty, size, iterator).
      int maxSize = maxSize();
      if (maxSize == 0) {
        return ImmutableSet.of();
      }
      ImmutableSet.Builder<@NonNull E> builder = ImmutableSet.builderWithExpectedSize(maxSize);
      for (E element : this) {

          Collection<V> valueCollection = keyToValueCollectionEntry.getValue();
          return CollectSpliterators.map(
              valueCollection.spliterator(),
              Spliterator.ORDERED | Spliterator.NONNULL | Spliterator.IMMUTABLE,
              (V value) -> immutableEntry(key, value));
        },
        Spliterator.SIZED | (this instanceof SetMultimap ? Spliterator.DISTINCT : 0),
        size());
  }

        Spliterator.SIZED
            | (entrySpliterator.characteristics()
                & (Spliterator.ORDERED | Spliterator.NONNULL | Spliterator.IMMUTABLE)),
        multiset.size());
  }

  /** An implementation of {@link Multiset#size}. */
  static int linearTimeSizeImpl(Multiset<?> multiset) {
    long size = 0;

import java.util.TreeMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.function.BinaryOperator;
import java.util.stream.Collector;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/**
 * Static utility methods pertaining to {@link Map} instances (including instances of {@link