* there's no way to assign a {@code @Nullable T} to a field {@code T foo;} and instruct the
   * analysis that that means "plain {@code T}" rather than the inferred type {@code @Nullable T}.
   * (And even if annotations on local variables were permitted as an optional hint, no annotation
   * would be the right tool for the job here: {@code @Nullable} is the annotation that we're trying

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

/**
 * GWT emulated version of {@link ImmutableList}. TODO(cpovirk): more doc
 *
 * @author Hayward Chan
 */
abstract class ForwardingImmutableList<E> extends ImmutableList<E> {

  ForwardingImmutableList() {}

  abstract List<E> delegateList();

  @Override
  public int indexOf(@Nullable Object object) {
    return delegateList().indexOf(object);

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

/**
 * Tests for {@link Functions}.
 *
 * @author Mike Bostock
 * @author Vlad Patryshev
 */
@GwtCompatible
@NullMarked
public class FunctionsTest extends TestCase {

  public void testIdentity_same() {
    Function<@Nullable String, @Nullable String> identity = Functions.identity();
    assertNull(identity.apply(null));

    Callable<@Nullable Void> callable =
        new Callable<@Nullable Void>() {
          @Override
          public @Nullable Void call() throws Exception {
            assertEquals(Thread.currentThread().getName(), newName.get());
            return null;
          }
        };
    Callables.threadRenaming(callable, newName).call();

 * @author Ben Yu
 * @since 12.0
 */
/*
 * A nullable bound would let users create a TypeParameter instance for a parameter with a nullable
 * bound. However, it would also let them create `new TypeParameter<@Nullable T>() {}`, which
 * wouldn't behave as users might expect. Additionally, it's not clear how the TypeToken API could
 * support even a "normal" `TypeParameter<T>` when `<T>` has a nullable bound. (See the discussion

  private static final Iterable<@Nullable Integer> iterableNull = Arrays.asList((Integer) null);
  private static final Iterable<@Nullable Integer> iterableNullNull =
      Arrays.asList((Integer) null, null);
  private static final Iterable<@Nullable Integer> iterableNull1 = Arrays.asList(null, 1);
  private static final Iterable<@Nullable Integer> iterable1Null = Arrays.asList(1, null);

import java.util.logging.Level;
import org.jspecify.annotations.Nullable;

/** Implementation of {@link Futures#immediateFuture}. */
@GwtCompatible
// TODO(cpovirk): Make this final (but that may break Mockito spy calls).
class ImmediateFuture<V extends @Nullable Object> implements ListenableFuture<V> {
  static final ListenableFuture<?> NULL = new ImmediateFuture<@Nullable Object>(null);

     * @return The interpolated string, or null if the input was null.
     */
    @Nullable
    String interpolate(
            @Nullable String val,
            @Nullable UnaryOperator<String> callback,
            @Nullable BinaryOperator<String> postprocessor,
            boolean defaultsToEmpty);

    /**

    }
  }

  @Override
  public @Nullable Entry<E> firstEntry() {
    return delegate().firstEntry();
  }

  /**
   * A sensible definition of {@link #firstEntry()} in terms of {@code entrySet().iterator()}.
   *
   * <p>If you override {@link #entrySet()}, you may wish to override {@link #firstEntry()} to
   * forward to this implementation.
   */
  protected @Nullable Entry<E> standardFirstEntry() {

  protected abstract ListeningExecutorService delegate();

  @Override
  public <T extends @Nullable Object> ListenableFuture<T> submit(Callable<T> task) {
    return delegate().submit(task);
  }

  @Override
  public ListenableFuture<?> submit(Runnable task) {
    return delegate().submit(task);
  }

  @Override
  public <T extends @Nullable Object> ListenableFuture<T> submit(
      Runnable task, @ParametricNullness T result) {