This code snippet shows you how to warm up the JVM before performing any benchmarks.

jvm_warmup.java

private static final int NUM_ITERATIONS = 100;

// ...

System.out.println("Warming up...");
for (int i = 1; i <= NUM_ITERATIONS; i++) {
  for (Node node : nodes) {
    Band<Float> band = createBand(Float.class);
    Random random = new Random();
    statsMap.put(band, new Stats(band, random.nextInt(200),
    random.nextFloat() * 10));
  }

  Collections.sort(new ArrayList<Stats<(statsMap.values()));
  statsMap.clear();
}

long totalRuntime = 0;
System.out.println("Benchmarking...");

for (int i = 1; i <= NUM_ITERATIONS; i++) {
  for (Node node : nodes) {
    Band<Float> band = createBand(Float.class);
    Random random = new Random();
    statsMap.put(band, new Stats(band, random.nextInt(200),
    random.nextFloat() * 10));
  }

  start = System.currentTimeMillis();
  Collections.sort(new ArrayList<Stats>(statsMap.values()));
  end = System.currentTimeMillis();

  System.out.println("Run #" + i + ": " + (end - start) + " ms");
  totalRuntime += (end - start);
  statsMap.clear();
}

double average = (totalRuntime / (double) NUM_ITERATIONS);
System.out.println("Average runtime: " + average + " ms");