this.unit = unit;
    }

    @Override
    public void run() {
      startTime = System.nanoTime();
      try {
        future.get(timeout, unit);
      } catch (Exception e) {
        // nothing
        exception = e;
      } finally {
        timeSpentBlocked = System.nanoTime() - startTime;
      }
    }

    void awaitWaiting() {
      while (!isBlocked()) {

      long end = System.nanoTime() + remainingNanos;

      while (true) {
        try {
          // TimeUnit.timedJoin() treats negative timeouts just like zero.
          NANOSECONDS.timedJoin(thread, remainingNanos);
          return;
        } catch (InterruptedException e) {
          interrupted = true;
          remainingNanos = end - System.nanoTime();
        }
      }
    } finally {

  long getRefreshNanos() {
    return (refreshNanos == UNSET_INT) ? DEFAULT_REFRESH_NANOS : refreshNanos;
  }

  /**
   * Specifies a nanosecond-precision time source for this cache. By default, {@link
   * System#nanoTime} is used.
   *
   * <p>The primary intent of this method is to facilitate testing of caches with a fake or mock
   * time source.
   *
   * @return this {@code CacheBuilder} instance (for chaining)

  long getRefreshNanos() {
    return (refreshNanos == UNSET_INT) ? DEFAULT_REFRESH_NANOS : refreshNanos;
  }

  /**
   * Specifies a nanosecond-precision time source for this cache. By default, {@link
   * System#nanoTime} is used.
   *
   * <p>The primary intent of this method is to facilitate testing of caches with a fake or mock
   * time source.
   *
   * @return this {@code CacheBuilder} instance (for chaining)

      // 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 (this) {
          if (nanos == expirationNanos) { // recheck for lost race
            T t = delegate.get();
            value = t;