* ListenableFuture}</a>.
 *
 * <p>This class is GWT-compatible.
 *
 * <h3>Purpose</h3>
 *
 * <p>The main purpose of {@code ListenableFuture} is to help you chain together a graph of
 * asynchronous operations. You can chain them together manually with calls to methods like {@link
 * Futures#transform(ListenableFuture, com.google.common.base.Function, Executor) Futures.transform}

 * ListenableFuture}</a>.
 *
 * <p>This class is GWT-compatible.
 *
 * <h3>Purpose</h3>
 *
 * <p>The main purpose of {@code ListenableFuture} is to help you chain together a graph of
 * asynchronous operations. You can chain them together manually with calls to methods like {@link
 * Futures#transform(ListenableFuture, com.google.common.base.Function, Executor) Futures.transform}

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * Java super source for ListenableFuture, implementing a structural thenable via a default method.
 * For restrictions, please refer to the documentation of the then() method.
 */
@ElementTypesAreNonnullByDefault
public interface ListenableFuture<V extends @Nullable Object> extends Future<V>, IThenable<V> {
  void addListener(Runnable listener, Executor executor);

  @SafeVarargs
  public static <V extends @Nullable Object> ListenableFuture<List<V>> allAsList(
      ListenableFuture<? extends V>... futures) {
    ListenableFuture<List<@Nullable V>> nullable =
        new ListFuture<V>(ImmutableList.copyOf(futures), true);
    // allAsList ensures that it fills the output list with V instances.
    @SuppressWarnings("nullness")
    ListenableFuture<List<V>> nonNull = nullable;
    return nonNull;
  }

  private interface Merger {

    ListenableFuture<List<String>> merged(ListenableFuture<String> a, ListenableFuture<String> b);

    Merger allMerger =
        new Merger() {
          @Override
          public ListenableFuture<List<String>> merged(
              ListenableFuture<String> a, ListenableFuture<String> b) {
            return allAsList(ImmutableSet.of(a, b));
          }

/** Test for {@link ListenableFuture}. */
public class ListenableFutureTest extends TestCase {
  public void testNoNewApis() throws Exception {
    assertWithMessage(
            "Do not add new methods to ListenableFuture. Its API needs to continue to match the"
                + " version we released in a separate artifact com.google.guava:listenablefuture.")
        .that(ListenableFuture.class.getDeclaredMethods())
        .asList()

      Future<V> future) {
    if (future instanceof ListenableFuture) {
      return (ListenableFuture<V>) future;
    }
    return new ListenableFutureAdapter<>(future);
  }

  /**
   * Submits a blocking task for the given {@link Future} to provide {@link ListenableFuture}
   * functionality.
   *
   * <p><b>Warning:</b> If the input future does not already implement {@code ListenableFuture}, the

  private static final String DATA1 = "data";

  public void testListenInPoolThreadReturnsSameFuture() throws Exception {
    ListenableFuture<String> listenableFuture = immediateFuture(DATA1);
    assertSame(listenableFuture, listenInPoolThread(listenableFuture));
  }

  private static class SingleCallListener implements Runnable {

    private boolean expectCall = false;

  private static final String DATA1 = "data";

  public void testListenInPoolThreadReturnsSameFuture() throws Exception {
    ListenableFuture<String> listenableFuture = immediateFuture(DATA1);
    assertSame(listenableFuture, listenInPoolThread(listenableFuture));
  }

  private static class SingleCallListener implements Runnable {

    private boolean expectCall = false;

public interface ListeningExecutorService extends ExecutorService {
  /**
   * @return a {@code ListenableFuture} representing pending completion of the task
   * @throws RejectedExecutionException {@inheritDoc}
   */
  @Override
  <T extends @Nullable Object> ListenableFuture<T> submit(Callable<T> task);

  /**
   * @return a {@code ListenableFuture} representing pending completion of the task
   * @throws RejectedExecutionException {@inheritDoc}