private ComparisonChain() {}

  /** Begins a new chained comparison statement. See example in the class documentation. */
  public static ComparisonChain start() {
    return ACTIVE;
  }

  private static final ComparisonChain ACTIVE =
      new ComparisonChain() {
        @SuppressWarnings("unchecked") // unsafe; see discussion on supertype
        @Override

      --ntasks;
      int active = 1;

      while (true) {
        Future<T> f = futureQueue.poll();
        if (f == null) {
          if (ntasks > 0) {
            --ntasks;
            futures.add(submitAndAddQueueListener(executorService, it.next(), futureQueue));
            ++active;
          } else if (active == 0) {
            break;
          } else if (timed) {

   * need to be signalled because it is not known which if any of them have waiters (and hasWaiters
   * can't be used reliably because of a check-then-act race). With our Monitor guards, we only
   * signal the first active guard that is satisfied. But the corresponding thread may have already
   * been interrupted and is waiting to reacquire the lock while still registered in activeGuards,

 *   <li>{@link #keys}, {@link #keySet}, {@link #values}, {@link #entries}, which are similar to the
 *       corresponding view collections of {@link Map}
 *   <li>and, notably, even the collection returned by {@link #get get(key)} is an active view of
 *       the values corresponding to {@code key}
 * </ul>
 *
 * <p>The collections returned by the {@link #replaceValues replaceValues} and {@link #removeAll

  long getExpireAfterAccessNanos() {
    return (expireAfterAccessNanos == UNSET_INT)
        ? DEFAULT_EXPIRATION_NANOS
        : expireAfterAccessNanos;
  }

  /**
   * Specifies that active entries are eligible for automatic refresh once a fixed duration has
   * elapsed after the entry's creation, or the most recent replacement of its value. The semantics