@VisibleForTesting
  void setNanoClock(NanoClock clock) {
    Preconditions.checkArgument(clock != null, "clock must not be null!");
    this.clock = clock;
  }
@ VisibleForTesting void setNanoClock ( NanoClock clock ) { Preconditions . checkArgument ( clock != null , "clock must not be null!" ) ; this . clock = clock ; }
Sets the clock to be used for determining when max total time has elapsed doing retries.