sleep(long millis, int nanos)

thread类中的sleep方法没有实现ns级别的睡眠

public static void sleep(long millis, int nanos)
    throws InterruptedException {
   
        if (millis < 0) {
   
            throw new IllegalArgumentException("timeout value is negative");
        }

        if (nanos < 0 || nanos > 999999) {
   
            throw new IllegalArgumentException(
                                "nanosecond timeout value out of range");
        }

        if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
   
            millis++;
        }

        sleep(millis);
    }

• 由jdk源码可知道，只是实现了四舍五入的功能
• 线程休眠的最小单位还是毫秒。
• 当第二个参数nanos大于0.5毫秒时或者小于1毫秒，进一位。
• 其余情况不进位。

 public final void wait(long timeout, int nanos) throws InterruptedException {
   
        if (timeout < 0) {
   
            throw new IllegalArgumentException("timeout value is negative");
        }

        if (nanos < 0 || nanos > 999999) {
   
            throw new IllegalArgumentException(
                                "nanosecond timeout value out of range");
        }

        if (nanos > 0) {
   
            timeout++;
        }

        wait(timeout);
    }

• wait类似