How to write a micro-benchmark in Java correctly? Pitfalls of JIT and optimizations

Hi everyone. I'm a beginner Java developer, and I need to measure the performance of two algorithm implementations: one uses `ArrayList`, the other uses a regular array. I wrote a simple test: ```java public class MyBenchmark { public static void main(String[] args) { long start = System.nanoTime(); for (int i = 0; i < 100000; i++) { // Code with ArrayList List list = new ArrayList<>(); for (int j = 0; j < 1000; j++) { list.add(j); } int sum = 0; for (int val : list) { sum += val; } } long end = System.nanoTime(); System.out.println("ArrayList time: " + (end - start)); start = System.nanoTime();