Simulation: space wasted due to records being page-aligned

PaginationWastedSizeSimulation.java

import java.util.ArrayList;
import java.util.OptionalDouble;
import java.util.concurrent.ThreadLocalRandom;

class PaginationWastedSizeSimulation {

  public static void main(final String[] args) {
    //Records of random size, with avg=averageRecordSize
    //Page of pageSize
    //If record doesn't fit page -- it is moved to the next page, remaining space on the first page
    // is 'wasted' (padding).
    //Q: How much space is 'wasted', on average?
    //
    //A: with record size random enough (poisson) avg(wasted) == avg(recordSize).
    //   With less random (less entropy) distributions avg(wasted) > 1/2 avg(recordSize)

    final double pageSize = 1;
    final double averageRecordSize = 0.01;
    final int pagesToSimulate = 10_000;

    final ArrayList<Double> wastedSizes = new ArrayList<>();
    double occupiedOnPage = 0;
    while (wastedSizes.size() < pagesToSimulate) {
      final double recordSize = generateRecordSizeCutoffGauss(averageRecordSize);
      if (occupiedOnPage + recordSize > pageSize) {
        final double wastedSpace = pageSize - occupiedOnPage;
        wastedSizes.add(wastedSpace);
        occupiedOnPage = recordSize;//move whole record to next page
      }
      else {
        occupiedOnPage += recordSize;
      }
    }

    final OptionalDouble averageReminder = wastedSizes.stream().mapToDouble(Double::doubleValue).average();
    System.out.printf("Average wasted space = %.3f of average record size per page\n",
                      averageReminder.orElse(0) / averageRecordSize);
  }

  private static double generateRecordSizeUniform(final double averageRecordSize) {
    final ThreadLocalRandom rnd = ThreadLocalRandom.current();
    return averageRecordSize + rnd.nextDouble(0, 0.5 * averageRecordSize);
  }

  private static double generateRecordSizeCutoffGauss(final double averageRecordSize) {
    final ThreadLocalRandom rnd = ThreadLocalRandom.current();
    while (true) {
      final double candidate = rnd.nextGaussian(averageRecordSize, averageRecordSize);
      if (candidate > 0) {
        return candidate;
      }
    }
  }
}