if (hashTable[(knownRunStart + maxRunBeforeFallback - 1) & mask] == null) {
            // There are only maxRunBeforeFallback - 1 elements between here and there,
            // so even if they were all nonnull, we wouldn't detect a hash flood.  Therefore,
            // we can skip them all.
            knownRunStart += maxRunBeforeFallback;
          } else {