因此,我编写了一个相当愚蠢的程序,只是为了稍微使用 nanoTime。我希望能够检查少量代码的执行时间,所以我认为 nanoTime 是最好的。我想确定这段代码的平均执行时间,所以我把它放在一个 for 循环中。然而,当在 for 循环中时,平均下降到大约 6,000 纳秒。我知道这对小代码来说并没有太大的区别,但我很好奇为什么对于相同的确切代码会有任何不同?这是产生不同时间的两个块:这个平均约为 8064 纳秒:
long start, end, totalTime;
double milliseconds, seconds, minutes, hours, days, years;
totalTime = 0;
start = System.nanoTime();
milliseconds = System.currentTimeMillis();
seconds = milliseconds/1000;
minutes = seconds/60;
hours = minutes/60;
days = hours/24;
years = days/365;
end = System.nanoTime();
totalTime = end-start;
这个平均约为 2200 纳秒:
long start, end, totalTime;
double milliseconds, seconds, minutes, hours, days, years;
totalTime = 0;
for(int i = 1; i < 11; i++){
start = System.nanoTime();
milliseconds = System.currentTimeMillis();
seconds = milliseconds/1000;
minutes = seconds/60;
hours = minutes/60;
days = hours/24;
years = days/365;
end = System.nanoTime();
totalTime += end-start;
System.out.println(end-start); //this was added to manually calc. the average to
//make sure the code was executing properly. does not effect execution time.
}
然后找到你所用的平均值 totalTime*.1