repeating a task for a length of time

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rebelbuttmunch - 02 May 2007 15:07 GMT

Hi,

What would be the best way to code a task so that it would run
iteratively for n seconds. For example, I have to code to fire a http
request, but I want to fire that request over and over for 60 seconds.
I was thinking about grabbing the time at the start and checking the
time after each loop, but it seems a bit innefficient.

Thanks!
Stephen.

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Daniel Pitts - 02 May 2007 15:36 GMT

> Hi,
>
> What would be the best way to code a task so that it would run
> iteratively for n seconds. For example, I have to code to fire a http
> request, but I want to fire that request over and over for 60 seconds.

So, your requirement (pseudo code)

for 60 second
make a request

in Java, that translates to

> I was thinking about grabbing the time at the start and checking the
> time after each loop, but it seems a bit innefficient.

long endTime = System.currentTimeMillis() + 60 * 1000;
while (endTime > System.currentTimeMillis()) {
makeRequest();
}

Whats inefficient about that? It does exactly what you want, and
nothing you don't. It would be a little different if you didn't do
anything in the while loop. Some people mistakenly use that as a
delay/sleep mechanism.

// BAD:
while (endTime > System.currentTimeMillis()) { /* do nothing */}

Hope this helps.
Daniel.

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Red Orchid - 02 May 2007 17:24 GMT

Daniel Pitts <googlegroupie@coloraura.com> wrote or quoted in
Message-ID <1178116602.911032.319830@y5g2000hsa.googlegroups.com>:

> long endTime = System.currentTimeMillis() + 60 * 1000;
> while (endTime > System.currentTimeMillis()) {
> makeRequest();
> }

I think that the following code is only proper for simple testing.

<code>
long startTime = System.currentTimeMillis();

... // code block #1

long endTime = System.currentTimeMillis();
long interval = endTime - startTime;
</code>

"interval" is unreliable value because "System.currentTimeMillis()"
returns current time of *system*. In other words, if system time
is set to 01/01/1970 during "#1", the value of "interval" is negative.

Modern clock programs have the function of automatic synchronization
with internet time server (e.g. clock on WinXP tray).

Reply to this Message

Daniel Pitts - 03 May 2007 02:49 GMT

> Daniel Pitts <googlegrou...@coloraura.com> wrote or quoted in
> Message-ID <1178116602.911032.319...@y5g2000hsa.googlegroups.com>:
[quoted text clipped - 21 lines]
> Modern clock programs have the function of automatic synchronization
> with internet time server (e.g. clock on WinXP tray).

How about System.nanoTime() then? That has a guaranty on the
difference between two calls, does it not?

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repeating a task for a length of time

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