*
 * <p>Occasionally, an API will return a plain {@code Future} and it will be impossible to change
 * the return type. For this case, we provide a more expensive workaround in {@code
 * JdkFutureAdapters}. However, when possible, it is more efficient and reliable to create a {@code
 * ListenableFuture} directly.
 *
 * @author Sven Mawson
 * @author Nishant Thakkar

Let's start with an example and then see it in detail.

We create an async function `lifespan()` with `yield` like this:

{* ../../docs_src/events/tutorial003_py39.py hl[16,19] *}

    testBytes(3, EXPECTED_THREE_BYTE_ROUNDTRIPPABLE_COUNT);
  }

  /**
   * Tests that round tripping of a sample of four byte permutations work. All permutations are
   * prohibitively expensive to test for automated runs. This method tests specific four-byte cases.
   */
  public void testIsWellFormed_4BytesSamples() {
    // Valid 4 byte.
    assertWellFormed(0xF0, 0xA4, 0xAD, 0xA2);
    // Bad trailing bytes

    CountingRemovalListener<Integer, Integer> removalListener = countingRemovalListener();
    IdentityLoader<Integer> loader = identityLoader();

    // Even numbers are free, odd are too expensive
    Weigher<Integer, Integer> evensOnly =
        new Weigher<Integer, Integer>() {
          @Override
          public int weigh(Integer k, Integer v) {
            return k % 2;
          }
        };

// simply converts positional arguments to NewReader() into a
// more flexible way to provide optional inputs. This is currently
// used by the FanOut API call mostly to disable expensive md5sum
// calculation repeatedly under hash.Reader.
type Options struct {
	MD5Hex     string
	SHA256Hex  string
	Size       int64
	ActualSize int64
	DisableMD5 bool
	ForceMD5   []byte
}

     * Holder object for values that cannot be null or empty (will be printed unconditionally). This
     * helps to shortcut most calls to isEmpty(), which is important because the check for emptiness
     * is relatively expensive. Use a subtype so this also doesn't need any extra storage.
     */
    private static final class UnconditionalValueHolder extends ValueHolder {}
  }

  private MoreObjects() {}

     * Holder object for values that cannot be null or empty (will be printed unconditionally). This
     * helps to shortcut most calls to isEmpty(), which is important because the check for emptiness
     * is relatively expensive. Use a subtype so this also doesn't need any extra storage.
     */
    private static final class UnconditionalValueHolder extends ValueHolder {}
  }

  private MoreObjects() {}

      //
      // We use two volatile reads. We could reduce this to one by
      // putting our fields into a holder class, but (at least on x86)
      // the extra memory consumption and indirection are more
      // expensive than the extra volatile reads.
      long nanos = expirationNanos;
      long now = System.nanoTime();
      if (nanos == 0 || now - nanos >= 0) {
        synchronized (lock) {

        }
      }
    } else {
      /*
       * We'll call the user callback or collect the values only when all inputs complete,
       * regardless of whether some failed. This lets us avoid calling expensive methods like
       * Future.get() when we don't need to (specifically, for whenAllComplete().call*()), and it
       * lets all futures share the same listener.
       *

Before Let's Encrypt, these **HTTPS certificates** were sold by trusted third parties.

The process to acquire one of these certificates used to be cumbersome, require quite some paperwork and the certificates were quite expensive.

But then **<a href="https://letsencrypt.org/" class="external-link" target="_blank">Let's Encrypt</a>** was created.