import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NavigableSet;
import java.util.SortedSet;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link NavigableSet} whose contents will never change, with many other important properties

         * halfSquare. (We have to deal with overflow, though.)
         *
         * If we treat halfSquare as an unsigned long, we know that
         *            sqrtFloor^2 <= x < (sqrtFloor + 1)^2
         * halfSquare - sqrtFloor <= x < halfSquare + sqrtFloor + 1
         * so |x - halfSquare| <= sqrtFloor.  Therefore, it's safe to treat x - halfSquare as a
         * signed long, so lessThanBranchFree is safe for use.
         */

  }

  public void testToOptionalSingleton() {
    assertThat(Stream.of(1).collect(MoreCollectors.toOptional())).hasValue(1);
  }

  public void testToOptionalNull() {
    Stream<@Nullable Object> stream = Stream.of((Object) null);
    try {
      stream.collect(MoreCollectors.toOptional());
      fail("Expected NullPointerException");
    } catch (NullPointerException expected) {
    }
  }

   */
  @GwtIncompatible // java.io.ObjectOutputStream
  @J2ktIncompatible
  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    stream.writeObject(keyComparator());
    stream.writeObject(valueComparator());
    Serialization.writeMultimap(this, stream);
  }

  @GwtIncompatible // java.io.ObjectInputStream
  @J2ktIncompatible

  @J2ktIncompatible
  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    Serialization.writeMultimap(this, stream);
  }

  @GwtIncompatible // java.io.ObjectOutputStream
  @J2ktIncompatible
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    expectedValuesPerKey = DEFAULT_VALUES_PER_KEY;

  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    stream.writeObject(countMap);
  }

  @J2ktIncompatible // serialization
  private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    @SuppressWarnings("unchecked") // reading data stored by writeObject

   * <p><b>Comparison to {@code java.util.Optional}:</b> this method has no equivalent in Java 8's
   * {@code Optional} class; use {@code
   * optionals.stream().filter(Optional::isPresent).map(Optional::get)} instead.
   *
   * <p><b>Java 9 users:</b> use {@code optionals.stream().flatMap(Optional::stream)} instead.
   *
   * @since 11.0 (generics widened in 13.0)
   */
  public static <T> Iterable<T> presentInstances(

 *       converter.reverse().convertAll(bs)}.
 *   <li>Use {@code converter} or {@code converter.reverse()} anywhere a {@link
 *       java.util.function.Function} is accepted (for example {@link java.util.stream.Stream#map
 *       Stream.map}).
 *   <li><b>Do not</b> call {@link #doForward} or {@link #doBackward} directly; these exist only to
 *       be overridden.
 * </ul>
 *
 * <h3>Example</h3>
 *
 * <pre>

  @Override
  @J2ktIncompatible // serialization
  Object writeReplace() {
    return new EnumSerializedForm<E>(delegate);
  }

  @J2ktIncompatible // serialization
  private void readObject(ObjectInputStream stream) throws InvalidObjectException {
    throw new InvalidObjectException("Use SerializedForm");
  }

  /*
   * This class is used to serialize ImmutableEnumSet instances.
   */
  @J2ktIncompatible // serialization

import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.NoSuchElementException;
import java.util.function.Function;
import java.util.stream.Collector;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A {@link RangeMap} whose contents will never change, with many other important properties