Java ScheduledThreadPoolBasedExecutor的执行顺序不正确

我使用ScheduledThreadPoolBasedExecutor来调度和执行callable。 根据：它以给定的延迟或（如果延迟相等）以FIFO顺序执行任务。为此，它甚至在实现中包含AtomicLong sequencer

我写了一个测试，它提交了很多计算素数的任务

public class MyCallable implements Callable<Boolean> {
    private static AtomicInteger counter = new AtomicInteger(0);
    private final long prNumber;
    private long callNanoTime;
    private LocalDateTime callLocalDateTime;
    private boolean isCalled = false;

    public MyCallable(long number) {
        this.prNumber = number;
    }

    public Boolean call() {
        callNanoTime = System.nanoTime();
        callLocalDateTime = LocalDateTime.now();
        isCalled = true;
        return isPrime(this.prNumber);
    }

    public boolean isCalled() {..}

    public long getCallNanoTime() {..}

    public LocalDateTime getCallLocalDateTime() {..}

    private boolean isPrime(long n) {..}
}

事实上，可调用的调度到更晚的时间是在之前执行的。如果我增加粒度（任务之间的间隔为5-10毫秒），一切都很好

初始化和调度：

public class ScheduledThreadPoolBasedExecutor implements Executor {
    private ScheduledExecutorService scheduledExecutorService;
    private AtomicLong counter = new AtomicLong(0);

    public ScheduledThreadPoolBasedExecutor() {
        scheduledExecutorService = Executors.newScheduledThreadPool(1);
    }

    @Override
    public void schedule(Callable callable, LocalDateTime localDateTime) {
        long value = counter.incrementAndGet();
        if (value % 100 == 0) {
            System.out.println(String.format("Schedule callable #%s", value));
        }
        long delay = ChronoUnit.MILLIS.between(LocalDateTime.now(), localDateTime);
        scheduledExecutorService.schedule(callable, delay, TimeUnit.MILLISECONDS);
    }
}

---

这种1-3ms的不一致性是由操作系统和ScheduledThreadPoolBasedExecutor不保证此类时间的顺序造成的吗？还是我用错了？

小更新：我发现，按照所需执行时间的增加顺序安排任务，一切都可以正常工作。Collections.shuffle导致测试失败。

public class ScheduledThreadPoolBasedExecutor implements Executor {
    private ScheduledExecutorService scheduledExecutorService;
    private AtomicLong counter = new AtomicLong(0);

    public ScheduledThreadPoolBasedExecutor() {
        scheduledExecutorService = Executors.newScheduledThreadPool(1);
    }

    @Override
    public void schedule(Callable callable, LocalDateTime localDateTime) {
        long value = counter.incrementAndGet();
        if (value % 100 == 0) {
            System.out.println(String.format("Schedule callable #%s", value));
        }
        long delay = ChronoUnit.MILLIS.between(LocalDateTime.now(), localDateTime);
        scheduledExecutorService.schedule(callable, delay, TimeUnit.MILLISECONDS);
    }
}