@AndroidIncompatible // depends on details of GC
  public void testFreesNextReference() {
    Iterator<Object> itr =
        new AbstractIterator<Object>() {
          @Override
          public Object computeNext() {
            return new Object();
          }
        };
    WeakReference<Object> ref = new WeakReference<>(itr.next());
    GcFinalization.awaitClear(ref);
  }

    assertEquals(1, Iterators.size(registry.getSubscribers(new Object())));
    assertEquals(1, Iterators.size(registry.getSubscribers(1)));

    registry.register(new IntegerSubscriber());
    assertEquals(3, Iterators.size(registry.getSubscribers("")));
    assertEquals(1, Iterators.size(registry.getSubscribers(new Object())));
    assertEquals(2, Iterators.size(registry.getSubscribers(1)));
  }

  static <V extends @Nullable Object, X extends Exception> V getChecked(
      Future<V> future, Class<X> exceptionClass) throws X {
    return getChecked(bestGetCheckedTypeValidator(), future, exceptionClass);
  }

  /** Implementation of {@link Futures#getChecked(Future, Class)}. */
  @CanIgnoreReturnValue
  @VisibleForTesting
  @ParametricNullness
  static <V extends @Nullable Object, X extends Exception> V getChecked(

        assertThat(map, is(notNullValue()));
        assertThat(map.isEmpty(), is(false));
        assertThat(map.get(Foo.class.getTypeParameters()[0]), is(sameClass(Object.class)));
    }

    /**
     * @throws Exception
     */
    public void testGenericMethod() throws Exception {
        final Map<TypeVariable<?>, Type> map = GenericsUtil.getTypeVariableMap(Fuga.class);

@ElementTypesAreNonnullByDefault
public final class Callables {
  private Callables() {}

  /** Creates a {@code Callable} which immediately returns a preset value each time it is called. */
  public static <T extends @Nullable Object> Callable<T> returning(@ParametricNullness T value) {
    return () -> value;
  }

  /**
   * Creates an {@link AsyncCallable} from a {@link Callable}.
   *

 * MoreExecutors#listeningDecorator}.
 *
 * @author Sven Mawson
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public class ListenableFutureTask<V extends @Nullable Object> extends FutureTask<V>
    implements ListenableFuture<V> {
  // TODO(cpovirk): explore ways of making ListenableFutureTask final. There are some valid reasons

 */
@GwtIncompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractNavigableMap<K extends @Nullable Object, V extends @Nullable Object>
    extends IteratorBasedAbstractMap<K, V> implements NavigableMap<K, V> {

  @Override
  @CheckForNull
  public abstract V get(@CheckForNull Object key);

  @Override
  @CheckForNull
  public Entry<K, V> firstEntry() {

    // it still should only have executed twice due to memoization
    assertEquals(2, countingSupplier.calls);
  }

  public void testOfInstanceSuppliesSameInstance() {
    Object toBeSupplied = new Object();
    Supplier<Object> objectSupplier = Suppliers.ofInstance(toBeSupplied);
    assertSame(toBeSupplied, objectSupplier.get());
    assertSame(toBeSupplied, objectSupplier.get()); // idempotent
  }

    // it still should only have executed twice due to memoization
    assertEquals(2, countingSupplier.calls);
  }

  public void testOfInstanceSuppliesSameInstance() {
    Object toBeSupplied = new Object();
    Supplier<Object> objectSupplier = Suppliers.ofInstance(toBeSupplied);
    assertSame(toBeSupplied, objectSupplier.get());
    assertSame(toBeSupplied, objectSupplier.get()); // idempotent
  }

    }

    @Override
    public void acceptAllColumnMap(Entity entity, Map<String, ? extends Object> allColumnMap) {
    }

    @Override
    public Map<String, Object> extractPrimaryKeyMap(Entity entity) {
        return null;
    }

    @Override
    public Map<String, Object> extractAllColumnMap(Entity entity) {
        return null;