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TimeUnit.sleep(long timeout)文档这样描述它的论点:
timeout - the minimum time to sleep.
但是,我发现 — 至少在带有 Java 8 update 141 的 Windows 7 64 位上 — 线程 hibernate 的时间通常少于:
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。然而,TimeUnit 文档还指出 TimeUnit.sleep()
是 Thread.sleep
的便利包装器,而后者没有说明它是否保证至少 sleep 指定数量。
这是一个 API 实现错误,还是 TimeUnit.sleep
和/或 Thread.sleep
设计为仅 hibernate 大约,而不是至少,指定的持续时间?