if (instance != null) {
      return (ListenableFuture<V>) instance;
    }
    return new ImmediateCancelledFuture<>();
  }

  /**
   * Executes {@code callable} on the specified {@code executor}, returning a {@code Future}.
   *
   * @throws RejectedExecutionException if the task cannot be scheduled for execution
   * @since 28.2
   */
  public static <O extends @Nullable Object> ListenableFuture<O> submit(

      @Override
      T transform(@ParametricNullness F from) {
        return function.apply(from);
      }
    };
  }

  /**
   * Advances {@code iterator} {@code position + 1} times, returning the element at the {@code
   * position}th position.
   *
   * @param position position of the element to return
   * @return the element at the specified position in {@code iterator}

   * }
   *
   * refactored so that messageExpression is moved to a separate String-returning method.
   *
   * if (guardExpression) {
   *    throw new BadException(badMsg(...));
   * }
   *
   * The alternative natural refactorings into void or Exception-returning methods are much slower.
   * This is a big deal - we're talking factors of 2-8 in microbenchmarks, not just 10-20%. (This is

    assertEquals(3, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());
    assertEquals(2, stats.hitCount());

    key = new Object();
    assertSame(value, cache.get(key, Callables.returning(value)));
    stats = cache.stats();
    assertEquals(3, stats.missCount());
    assertEquals(4, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());
    assertEquals(2, stats.hitCount());

   *
   * <p>When the weight of an entry is zero it will not be considered for size-based eviction
   * (though it still may be evicted by other means).
   *
   * <p><b>Important note:</b> Instead of returning this as a {@code CacheBuilder}
   * instance, this method returns {@code CacheBuilder<K1, V1>}. From this point on, either the
   * original reference or the returned reference may be used to complete configuration and build

		if !isErrBucketNotFound(err) {
			storageLogOnceIf(ctx, err, "erasure-list-objects-path-"+bucket)
		}
		return loi, toObjectErr(err, bucket)
	}
	defer merged.truncate(0) // Release when returning

	if contextCanceled(ctx) {
		return ListObjectVersionsInfo{}, ctx.Err()
	}

	if versionMarker == "" {
		o := listPathOptions{Marker: marker}

    assertNoExpectedFailures();
    super.tearDown();
  }

  public void testFrom() throws Exception {
    ClosingFuture<String> closingFuture =
        ClosingFuture.from(executor.submit(Callables.returning(closeable1)))
            .transform(
                new ClosingFunction<TestCloseable, String>() {
                  @Override

        this.retryOnConnectionFailure = retryOnConnectionFailure
      }

    /**
     * Configure this client to perform fast fallbacks by attempting multiple connections
     * concurrently, returning once any connection connects successfully.
     *
     * This implements Happy Eyeballs ([RFC 6555][rfc_6555]), balancing connect latency vs.
     * wasted resources.
     *

  private abstract static class RawTypeConsistencyTester<T extends Enum<T> & CharSequence> {
    abstract T returningT();

    abstract void acceptT(T t);

    abstract <X extends T> X returningX();

    abstract <X> void acceptX(X x);

    abstract <T2 extends Enum<T2> & CharSequence> T2 returningT2();

    abstract <T2 extends CharSequence & Iterable<T2>> void acceptT2(T2 t2);

    inappropriate.

 *  New: `HttpUrl.get(String)` is an alternative to `HttpUrl.parse(String)` that throws an exception
    when the URL is malformed instead of returning null. Use this to avoid checking for null in
    situations where the input is known to be well-formed. We've also added `MediaType.get(String)`
    which is an exception-throwing alternative to `MediaType.parse(String)`.