JavaThread.sleep最短时间[重复]

Question

时间单位睡眠（长超时）文档这样描述其参数：

超时 - 最小睡眠时间。

但是，我发现 - 至少在Windows 7 64位Java 8更新141上 - 线程的睡眠时间通常低于最低要求：

public static void main(String[] args) throws InterruptedException {
    final long from = TimeUnit.MILLISECONDS.toNanos(100);
    final long to   = TimeUnit.MILLISECONDS.toNanos(1000);
    final long step = TimeUnit.MILLISECONDS.toNanos(100);
    for (long requestedSleepDuration = from; requestedSleepDuration < to; requestedSleepDuration += step) {
        long sleepStartTime = System.nanoTime();
        TimeUnit.NANOSECONDS.sleep(requestedSleepDuration);
        long sleepEndTime = System.nanoTime();
        System.out.printf(
                "requested=%9d  actual=%9d  %s%n",
                requestedSleepDuration,
                sleepEndTime - sleepStartTime,
                (sleepEndTime - sleepStartTime >= requestedSleepDuration ? "OK" : " Slept less than minimum!"));
    }
}

典型输出：

requested=100000000  actual= 99534864  Slept less than minimum!
requested=200000000  actual=200063646  OK
requested=300000000  actual=299223086  Slept less than minimum!
requested=400000000  actual=399598620  Slept less than minimum!
requested=500000000  actual=499910360  Slept less than minimum!
requested=600000000  actual=600028523  OK
requested=700000000  actual=699604816  Slept less than minimum!
requested=800000000  actual=799230602  Slept less than minimum!
requested=900000000  actual=899490648  Slept less than minimum!

这似乎与文件相矛盾。然而，TimeUnit文档还声明< code>TimeUnit.sleep()是< code>Thread.sleep的便利包装器，后者没有说明它是否保证至少睡眠指定的时间。

这是 API 实现错误，还是时间单元睡眠和/或线程睡眠被设计为仅Hibernate大约而不是至少指定的持续时间？

Answer 1

TimeUnit（时间单位）。sleep（）委托给Thread.sleep（）。

Thread.sleep（）受制于系统计时器和调度程序的精度和准确性，因此TimeUnit.sleep（）不会像您需要的那样准确。