Why does Thread.Sleep() method sleep more than expected?

Question

So, my program is basically creating a child thread of Main and get an integer as an input from the user, and convert that number to milisecond by timing it by 1000.

But in the for loop, Thread.Sleep() sleeps about 10 seconds, when I typed number 5 as an input.

The code:

static void CallToChildThread()
{

     Console.WriteLine("How many seconds do you want this thread to rest?");
     int time = Convert.ToInt32(Console.Read());
     int mili = time * 1000;

     for (int i = 0; i < time; i++)
     {
         Console.Write(". ");
         Thread.Sleep(mili);
     }

     Console.WriteLine();

}

So, when I typed 5, and the code will multiply 5 by 1000 and 5000 will be stored in mili.

But, in the for loop, when the Thread.Sleep(mili) is executed, it doesn't sleep whole 5 seconds, it sleeps 10 seconds, when it iterates once through the loop.

Also, when I change substitute mili with 5000 to make the thread sleep for 5 seconds, each time it loops, and it worked, but the loop iterated more than I expected. For example, this is the input I typed:

How many seconds do you want this thread to rest?
5

. . . . . . . . . .

It counts 5 seconds properly each time it iterates. But it iterated more than 5. If I typed 5 then shouldn't the for loop iterate 5 times and abort? Showing only 5 periods?

I don't think this is a duplicate in this case. If it was milliseconds off, then yes. Seconds... no. — CodingWithSpike, Jul 05 '14 at 23:00
@Steve Yes, I tried it, then I get an unhandled exception: System.FormatException. — James, Jul 05 '14 at 23:00
@Steve All I typed was number 5 and two new lines. I have no idea why, but I had to press enter twice to send the input.. — James, Jul 05 '14 at 23:05
Why don't you try stepping through the code with a debugger? — LVBen, Jul 05 '14 at 23:23
I don't know if we can undo the close as duplicate, but it isn't at all. The problem is: `Convert.ToInt32(Console.Read());` The value returned from `Console.Read()` is an int, which is the ASCII value of the character. For example '1' is changed to its ASCII value of 49. It then sleeps for 49 seconds instead of 1. Instead, use `int time = Int32.Parse(Console.ReadLine());` — CodingWithSpike, Jul 05 '14 at 23:23

AlexD · Accepted Answer · 2014-07-05T23:16:00.053

6

Console.Read() reads a character, and then you convert it's ASCII code to int.

This prints 53 if you enter 5:

Console.WriteLine("{0}", Console.Read());

BTW, you multiply 5 by 1000, and then sleep for already multiplied value. So the overall time of sleeping in the loop seems to be 5 * 5 * 1000, not 5 * 1000 ms. Is it intentional?

edited Jul 05 '14 at 23:16

answered Jul 05 '14 at 22:54

AlexD

32,156
3
71
65

Yes, I tried Console.ReadLine(), but I get an unhandled exception: System.FormatException. Do you know why? – James Jul 05 '14 at 23:06

score 3 · Answer 2 · answered Jul 05 '14 at 23:04

3

You need to use Console.ReadLine() instead of Console.Read():

int time = Convert.ToInt32(Console.ReadLine());

answered Jul 05 '14 at 23:04

David

325
3
12

Why does Thread.Sleep() method sleep more than expected?

2 Answers2