Test accuracy of ScheduledThreadPoolExecutor.

Main.java

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.LockSupport;

// Run with enough heap and -verbose:gc to make sure that GC is not running.
public class Main {

    static final int RUNS = 10_000;

    static final ScheduledExecutorService service = Executors.newScheduledThreadPool(1);
    static final List<Long> deltas = new ArrayList<>(RUNS);

    static void doSchedule() {
        deltas.clear();
        for (int i = 0; i < RUNS; i++) {
            service.schedule(new Runnable() {

                final long start = System.nanoTime();

                public void run() {
                    deltas.add(System.nanoTime() - start);
                }
            }, 1, TimeUnit.NANOSECONDS);
        }

        while (deltas.size() != RUNS) {
            LockSupport.parkNanos(1000);
        }
    }

    public static void main(String... args) {

        // Run 100 warmups.
        for (int i = 0; i < 100; i++) {
            doSchedule();
        }

        LockSupport.parkNanos(1000_000_000);

        doSchedule();

        long max = 0, min = Long.MAX_VALUE, avg = 0, median = 0;
        for (long delta : deltas) {
            max = Math.max(max, delta);
            min = Math.min(min, delta);
            avg += delta;
        }

        avg /= RUNS;

        Collections.sort(deltas);

        median = deltas.get(deltas.size() / 2);

        System.out.printf("max: %d, min: %d, avg: %d, median: %d, runs: %d\n", max, min, avg, median, RUNS);

        service.shutdown();
    }
}