java 运行循环 5 分钟
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running loop for 5 minutes
提问by sjain
I have a requirment to run a while loop the 5 min.
I looked for the timer api but I could not found to do this.
Can any one provide a code snipet for this.
Thanks
我需要在 5 分钟内运行一段时间循环。我寻找了计时器 api，但我找不到这样做。任何人都可以为此提供代码片段。
谢谢
回答by sleske
The easiest way will be to just check how much time has elapsed on each iteration. Example:
最简单的方法是检查每次迭代已经过去了多少时间。例子：
final long NANOSEC_PER_SEC = 1000l*1000*1000;
long startTime = System.nanoTime();
while ((System.nanoTime()-startTime)< 5*60*NANOSEC_PER_SEC){
// do stuff
}
This will run the loop, until more than 5 minutes have elapsed.
这将运行循环，直到超过 5 分钟过去。
Notes:
笔记：
- The current loop iteration will always complete, so in practice it will always run for a bit more than 5 minutes.
- For this application
System.nanoTime()is more suitable thanSystem.currentTimeMillis()because the latter will change if the computer's system clock is adjusted, thus throwing off the calculation. Thanks to Shloim for pointing this out.
- 当前循环迭代将始终完成，因此在实践中它始终会运行 5 分钟多一点。
- 对于此应用程序
System.nanoTime()更合适，System.currentTimeMillis()因为如果调整计算机的系统时钟，后者会发生变化，从而中断计算。感谢 Shloim 指出这一点。
回答by Shloim
This loop will run for 5 minutes. It will not be effected by changes made to the computer's date/time (either by user or by NTP).
此循环将运行 5 分钟。它不会受到对计算机日期/时间所做的更改（由用户或 NTP）影响。
long endTime = System.nanoTicks() + TimeUnit.NANOSECONDS.convert(5L, TimeUnit.MINUTES);
while ( System.nanoTicks() < endTime ){
// do whatever
}
Other methods like System.currentTimeMillis()should be avoided, because they rely on the computer date/time.
System.currentTimeMillis()应该避免使用其他方法，因为它们依赖于计算机日期/时间。
回答by Waldheinz
Because you are talking about the timer API I guess what you are after is a delay instead of a "loop running for 5min". If this is the case you could use something like Thread.sleep(..)which would allow to let the CPU do more usefull stuff that busy-waiting. Or at least save some energy and the planet.
因为您在谈论计时器 API，所以我猜您所追求的是延迟而不是“循环运行 5 分钟”。如果是这种情况，您可以使用Thread.sleep(..) 之类的东西，它可以让 CPU 做更多有用的事情，而不是忙着等待。或者至少节省一些能源和地球。
