SettableFuture<String> f = SettableFuture.create();
    Exception e = new IllegalArgumentException("foo not found");
    MockCallback callback = new MockCallback(e);
    addCallback(f, callback, directExecutor());
    f.setException(e);
  }

  public void testCancel() {
    SettableFuture<String> f = SettableFuture.create();
    FutureCallback<String> callback =
        new FutureCallback<String>() {

    SettableFuture<String> f = SettableFuture.create();
    Exception e = new IllegalArgumentException("foo not found");
    MockCallback callback = new MockCallback(e);
    addCallback(f, callback, directExecutor());
    f.setException(e);
  }

  public void testCancel() {
    SettableFuture<String> f = SettableFuture.create();
    FutureCallback<String> callback =
        new FutureCallback<String>() {

    // ------------------------------------------------------------------------

    public boolean hasExceptions() {
        return exceptions != null && !exceptions.isEmpty();
    }

    public List<Exception> getExceptions() {
        return exceptions == null ? Collections.emptyList() : Collections.unmodifiableList(exceptions);
    }

    // ------------------------------------------------------------------------

    // ------------------------------------------------------------------------

    public boolean hasExceptions() {
        return exceptions != null && !exceptions.isEmpty();
    }

    public List<Exception> getExceptions() {
        return exceptions == null ? Collections.emptyList() : Collections.unmodifiableList(exceptions);
    }

    // ------------------------------------------------------------------------

    T fallbackResult;
    try {
      fallbackResult = doFallback(localFallback, castThrowable);
    } catch (Throwable t) {
      restoreInterruptIfIsInterruptedException(t);
      setException(t);
      return;
    } finally {
      exceptionType = null;
      fallback = null;
    }

    setResult(fallbackResult);
  }

                System.err.println("Missing: " + artifact);
            }
        }

        if (result.hasExceptions()) {
            for (Exception e : result.getExceptions()) {
                e.printStackTrace();
            }
        }
    }

    /**
     * Gets the exceptions that occurred while building the dependency graph.
     *
     * @return the exceptions that occurred, never {@code null}
     */
    @Nonnull
    List<Exception> getExceptions();

    /**
     * Gets the root node of the dependency graph.
     *
     * @return the root node of the dependency graph or {@code null} if none
     */
    @Nullable
    Node getRoot();

    /**

 * to set the result of the computation through the protected methods {@link #set(Object)}, {@link
 * #setFuture(ListenableFuture)} and {@link #setException(Throwable)}. Subclasses may also override
 * {@link #afterDone()}, which will be invoked automatically when the future completes. Subclasses
 * should rarely override other methods.
 *
 * @author Sven Mawson

          /*
           * We fail this `ListenableFuture`, whose result is exposed to the user through the
           * `ListenableScheduledTask` we return from the `schedule*` methods.
           */
          setException(t);

          /*
           * We fail the current run of the recurring task so that it is not rescheduled. This also
           * fails the `ScheduledFuture`, which might be visible only to users who operate directly

   *
   * <ul>
   *   <li>{@code null} initial state, nothing has happened.
   *   <li>{@link Cancellation} terminal state, {@code cancel} was called.
   *   <li>{@link Failure} terminal state, {@code setException} was called.
   *   <li>{@link DelegatingToFuture} intermediate state, {@code setFuture} was called.
   *   <li>{@link #NULL} terminal state, {@code set(null)} was called.