import java.util.Collections;
import java.util.Set;
import org.jspecify.annotations.Nullable;

/** Implementation of an {@link Optional} not containing a reference. */
@GwtCompatible
final class Absent<T> extends Optional<T> {
  static final Absent<Object> INSTANCE = new Absent<>();

  @SuppressWarnings("unchecked") // implementation is "fully variant"
  static <T> Optional<T> withType() {

    throwIf(closed);
    return options.contains(TestOption.AVAILABLE_ALWAYS_ZERO) ? 0 : in.available();
  }

  @Override
  public void close() throws IOException {
    closed = true;
    throwIf(CLOSE_THROWS);
    in.close();
  }

  private void throwIf(TestOption option) throws IOException {
    throwIf(options.contains(option));
  }

import java.util.SortedSet;
import org.jspecify.annotations.Nullable;

/**
 * Implementation of {@link Multisets#unmodifiableSortedMultiset(SortedMultiset)} for GWT.
 *
 * @author Louis Wasserman
 */
final class UnmodifiableSortedMultiset<E extends @Nullable Object> extends UnmodifiableMultiset<E>
    implements SortedMultiset<E> {
  UnmodifiableSortedMultiset(SortedMultiset<E> delegate) {
    super(delegate);
  }

  @Override

 * <p>In addition to {@link #execute}, subclasses must implement all methods related to shutdown and
 * termination.
 *
 * @author Chris Povirk
 * @since 14.0
 */
@CheckReturnValue
@GwtIncompatible
public abstract class AbstractListeningExecutorService extends AbstractExecutorService
    implements ListeningExecutorService {
  /** Constructor for use by subclasses. */
  public AbstractListeningExecutorService() {}

  /**

@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class MultimapToStringTester<K, V> extends AbstractMultimapTester<K, V, Multimap<K, V>> {
  @CollectionSize.Require(ZERO)
  @CollectionFeature.Require(absent = NON_STANDARD_TOSTRING)
  public void testToStringEmpty() {

@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.
@SuppressWarnings("JUnit4ClassUsedInJUnit3")
public class MultimapValuesTester<K, V> extends AbstractMultimapTester<K, V, Multimap<K, V>> {
  public void testValues() {
    List<V> expected = new ArrayList<>();
    for (Entry<K, V> entry : getSampleElements()) {

 *
 * @author Chris Povirk
 * @author Jared Levy
 * @author George van den Driessche
 * @author Louis Wasserman
 */
@GwtCompatible
@NullMarked
public abstract class TestStringBiMapGenerator implements TestBiMapGenerator<String, String> {

  @Override
  public SampleElements<Entry<String, String>> samples() {
    return new SampleElements<>(
        mapEntry("one", "January"),

import junit.framework.TestCase;
import org.jspecify.annotations.NullUnmarked;

/**
 * Unit test for {@link Charsets}.
 *
 * @author Mike Bostock
 */
@GwtCompatible
@NullUnmarked
public class CharsetsTest extends TestCase {

  @J2ktIncompatible
  @GwtIncompatible // Non-UTF-8 Charset
  public void testUsAscii() {
    assertThat(Charsets.US_ASCII).isEqualTo(Charset.forName("US-ASCII"));
  }

import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Tests for {@link Tables}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@NullMarked
public class TablesTest extends TestCase {
  @GwtIncompatible // SerializableTester
  public void testImmutableEntrySerialization() {
    Cell<String, Integer, Character> entry = immutableCell("foo", 1, 'a');

import java.io.Serializable;
import org.jspecify.annotations.NonNull;
import org.jspecify.annotations.Nullable;

/** An ordering that treats {@code null} as less than all other values. */
@GwtCompatible
final class NullsFirstOrdering<T extends @Nullable Object> extends Ordering<@Nullable T>
    implements Serializable {
  final Ordering<? super T> ordering;

  NullsFirstOrdering(Ordering<? super T> ordering) {