public long stdDev(){
  final long m=deltaCount.get() - 1;
  return m > 0 ? (long)Math.sqrt(deltaStdDev.get() / (double)m) : 0;
}

public long stdDev ( ) { final long m = deltaCount . get ( ) - 1 ; return m > 0 ? ( long ) Math . sqrt ( deltaStdDev . get ( ) / ( double ) m ) : 0 ; }
get ( approximate ) running - standard - deviation of time - delta , in nanoseconds .
