code: public void record(double amount) {
      if (amount >= 0.0) {
        add(totalAmount, amount);
        add(totalOfSquares, amount * amount);
        max(max, amount);
        count.incrementAndGet();
        lastUpdateTime.set(clock.wallTime());
      }
    }
docs: Updates the statistics kept by the summary with the specified amount.
  
  @param amount
  Amount for an event being measured. For example, if the size in bytes of responses
  from a server. If the amount is less than 0 the value will be dropped.