MutableDistribution.java 文件源码

public void add(double value, long numSamples) {
  checkArgument(numSamples >= 0, "numSamples must be non-negative");
  checkDouble(value);

  // having numSamples = 0 works as expected (does nothing) even if we let it continue, but we
  // can short-circuit it by returning early.
  if (numSamples == 0) {
    return;
  }

  Map.Entry<Range<Double>, Long> entry = intervalCounts.getEntry(value);
  intervalCounts.put(entry.getKey(), entry.getValue() + numSamples);
  this.count += numSamples;

  // Update mean and sumOfSquaredDeviation using Welford's method
  // See Knuth, "The Art of Computer Programming", Vol. 2, page 232, 3rd edition
  double delta = value - mean;
  mean += delta * numSamples / count;
  sumOfSquaredDeviation += delta * (value - mean) * numSamples;
}