jainsahab

package com.google.cloud.datastore;
 
import com.google.cloud.datastore.StructuredQuery.PropertyFilter;
import com.google.cloud.datastore.aggregation.Aggregation;
import com.google.common.collect.Iterables;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

jainsahab

JMH -  Java Microbenchmark Harness
Why? - JMH takes care of the things like JVM warm-up and code-optimization paths.
JMH plugin in build.gradle
Benchmark annotation
Benchmark types
Warmup and actual Measurement
Dead code elimination - return statement / blackhole consume

jainsahab

import kotlin.math.sqrt

fun mean(array: DoubleArray): Double {
  return array.sum() / array.size.toDouble()
}

fun stdDeviation(array: DoubleArray): Double {
  val mean = mean(array)
  return sqrt(array.map { it - mean }.map { it * it }.sum() / (array.size - 1).toDouble())
}