*       Future} is "completed" even if it is cancelled while its underlying work continues on a
 *       thread, an RPC, etc. The {@code Future} is also "completed" if it fails "early" -- for
 *       example, if the deadline expires on a {@code Future} returned from {@link
 *       Futures#withTimeout} while the {@code Future} it wraps continues its underlying work. So
 *       beware: <i>Your {@code AsyncCallable} should not complete its {@code Future} until it is

   *
   * <ol>
   *   <li>calls {@link ExecutorService#shutdown()}, disabling acceptance of new submitted tasks.
   *   <li>awaits executor service termination for half of the specified timeout.
   *   <li>if the timeout expires, it calls {@link ExecutorService#shutdownNow()}, cancelling
   *       pending tasks and interrupting running tasks.
   *   <li>awaits executor service termination for the other half of the specified timeout.
   * </ol>
   *

      return true;
    }
  },

  /**
   * The entry's expiration timestamp has passed. This can occur when using {@link
   * CacheBuilder#expireAfterWrite} or {@link CacheBuilder#expireAfterAccess}.
   */
  EXPIRED {
    @Override
    boolean wasEvicted() {
      return true;
    }
  },

  /**
   * The entry was evicted due to size constraints. This can occur when using {@link

      // (Or it's a weird case like a LinkedList in a Cache<ArrayList, ...>, but *shrug*.)
      @SuppressWarnings("unchecked")
      K castKey = (K) key;
      alertListenerIfPresent(castKey, value.getValue(), RemovalCause.EXPIRED);
      cachingHashMap.remove(key);
      return null;
    }
  }

  @CanIgnoreReturnValue
  @Override
  public V put(K key, V value) {
    checkNotNull(key);
    checkNotNull(value);

                // This is a duplicate check, as preWriteCleanup already purged expired
                // entries, but let's accommodate an incorrect expiration queue.
                enqueueNotification(
                    entryKey, hash, value, valueReference.getWeight(), RemovalCause.EXPIRED);
              } else {
                recordLockedRead(e, now);
                statsCounter.recordHits(1);

   * specified {@code timeout}, or returns {@code false} immediately (without waiting) if the permit
   * would not have been granted before the timeout expired.
   *
   * <p>This method is equivalent to {@code tryAcquire(1, timeout, unit)}.
   *
   * @param timeout the maximum time to wait for the permit. Negative values are treated as zero.

  }

  /**
   * Returns a future that delegates to another but will finish early (via a {@link
   * TimeoutException} wrapped in an {@link ExecutionException}) if the specified duration expires.
   *
   * <p>The delegate future is interrupted and cancelled if it times out.
   *
   * @param delegate The future to delegate to.
   * @param unit the time unit of the time parameter

 *
 * <p>Valid:
 *
 * <ul>
 *   <li>Live: valid key/value are set
 *   <li>Loading: loading is pending
 * </ul>
 *
 * <p>Invalid:
 *
 * <ul>
 *   <li>Expired: time expired (key/value may still be set)
 *   <li>Collected: key/value was partially collected, but not yet cleaned up
 *   <li>Unset: marked as unset, awaiting cleanup or reuse
 * </ul>
 */
@GwtIncompatible

      return true;
    }
  },

  /**
   * The entry's expiration timestamp has passed. This can occur when using {@link
   * CacheBuilder#expireAfterWrite} or {@link CacheBuilder#expireAfterAccess}.
   */
  EXPIRED {
    @Override
    boolean wasEvicted() {
      return true;
    }
  },

  /**
   * The entry was evicted due to size constraints. This can occur when using {@link

    // then we know it must have given a pending toString value earlier. If not, then the future
    // completed after the timeout expired, and the message might be success.
    if (isDone()) {
      throw new TimeoutException(message + " but future completed as timeout expired");
    }
    throw new TimeoutException(message + " for " + futureToString);
  }

  /**
   * {@inheritDoc}
   *