return LexicographicalComparatorHolder.PureJavaComparator.INSTANCE;
  }

  /**
   * Provides a lexicographical comparator implementation; either a Java implementation or a faster
   * implementation based on {@link Unsafe}.
   *
   * <p>Uses reflection to gracefully fall back to the Java implementation if {@code Unsafe} isn't
   * available.
   */
  @VisibleForTesting
  static class LexicographicalComparatorHolder {

 *       worse, and possibly better, than creating a mutable collection and copying it.
 *   <li>Implementations generally do not cache hash codes. If your element or key type has a slow
 *       {@code hashCode} implementation, it should cache it itself.
 * </ul>
 *
 * <h4>Example usage</h4>
 *
 * <pre>{@code
 * class Foo {

      }
      return max(estimatedSize, 0);
    }

    @Override
    public final int characteristics() {
      return characteristics;
    }
  }

  /**
   * Implementation of {@link Stream#flatMap} with an object spliterator output type.
   *
   * <p>To avoid having this type, we could use {@code FlatMapSpliterator} directly. The main

import java.util.Collections;
import java.util.Iterator;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * A utility for testing an Iterator implementation by comparing its behavior to that of a "known
 * good" reference implementation. In order to accomplish this, it's important to test a great
 * variety of sequences of the {@link Iterator#next}, {@link Iterator#hasNext} and {@link

import java.util.HashMap;
import java.util.Map;
import java.util.function.BiConsumer;
import javax.annotation.CheckForNull;
import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Implementation of ImmutableMap backed by a JDK HashMap, which has smartness protecting against
 * hash flooding.
 */
@GwtCompatible(emulated = true)
@ElementTypesAreNonnullByDefault

  /**
   * Invoked to request the service to stop.
   *
   * <p>By default this method does nothing.
   *
   * <p>Currently, this method is invoked while holding a lock. If an implementation of this method
   * blocks, it can prevent this service from changing state. If you need to performing a blocking
   * operation in order to trigger shutdown, consider instead registering a listener and

   * ImmutableEnumSet/ImmutableSortedSet, regardless of implementation type. It
   * captures their "logical contents" and they are reconstructed using public
   * static factories. This is necessary to ensure that the existence of a
   * particular implementation type is an implementation detail.
   */
  @J2ktIncompatible // serialization

import java.util.Set;
import org.junit.Ignore;

/**
 * Tests {@link java.util.Map#entrySet}.
 *
 * @author Louis Wasserman
 * @param <K> The key type of the map implementation under test.
 * @param <V> The value type of the map implementation under test.
 */
@GwtCompatible
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.

import java.util.Set;
import org.junit.Ignore;

/**
 * Tests {@link java.util.Map#entrySet}.
 *
 * @author Louis Wasserman
 * @param <K> The key type of the map implementation under test.
 * @param <V> The value type of the map implementation under test.
 */
@GwtCompatible
@Ignore // Affects only Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.

        }
      }
    }
    return -1;
  }

  /** Returns an implementation of {@link List#listIterator(int)}. */
  static <E extends @Nullable Object> ListIterator<E> listIteratorImpl(List<E> list, int index) {
    return new AbstractListWrapper<>(list).listIterator(index);
  }

  /** An implementation of {@link List#subList(int, int)}. */
  static <E extends @Nullable Object> List<E> subListImpl(