TimeUnit.sleep(long timeout)文档描述了它的论点:
超时 - 最短睡眠时间。
但是,我发现 - 至少在带有Java 8更新141的Windows 7 64位上 - 线程通常会睡眠少而不是最小值:
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!
这似乎与文档相矛盾。但是,TimeUnit文档还指出TimeUnit.sleep()
是Thread.sleep
的便利包装器,而后者并未说明它是否保证至少睡眠时间为。{/ p>
这是一个API实现错误,还是TimeUnit.sleep
和/或Thread.sleep
设计为只为大约而不是至少休眠,指定的持续时间?
答案 0 :(得分:3)
TimeUnit.sleep()
代表Thread.sleep()
。
Thread.sleep()
受制于系统计时器和计划程序的精确性和准确性,因此TimeUnit.sleep()
不会像您需要的那样准确。