Rounding an int number to another int number

Question

while(potatosconeflour <= c1) { potatosconeflour = potatosconeflour + potatosconeflour; }

I used a while loop which does not work after inputting the number 24.I am trying to round an int number to another int number. E.g., I want to round any number to a multiple of 8.

E.g: rounding 1 to 8, 13 to 16, 23 to 24

Hello and welcome to stackoverflow! Please show us some more of your code - the current excerpt isn't sufficient to find the problem. — Maurice
– Maurice, Commented Dec 21, 2016 at 21:27

Mureinik · Accepted Answer · 2016-12-21 21:38:36Z

5

I'd divide the source number by the number to round it by (caution: cast it to a double so you don't use integer division!) use Math.ceil to round the result upwards, and then multiply it back by the same number:

public static int roundToMultiple(int toRound, int roundBy) { return roundBy * (int) Math.ceil((double)toRound / roundBy); }

edited Dec 21, 2016 at 21:38

answered Dec 21, 2016 at 21:21

Mureinik

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3 Comments

Marcelo Over a year ago

This is wrong. You can't use Math.round, roundToMultiple(1,8) will return 0

Marcelo Over a year ago

Math.round rounds to the nearest int, so 1/8 will get rounded to 0 and then 0 * 8 = 0. You need to use Math.ceil instead

Mureinik Over a year ago

@Marcelo you're right. The OP used the term round, although he actually meant ceiling, which threw me off. I've edited my answer accordingly.

Louis Wasserman · Accepted Answer · 2016-12-21 22:00:07Z

3

If you want to round to the nearest multiple of 8, that's just ((i + 3) / 8) * 8. (That rounds down if it's 8n + 4. If you want to round up from half, use i + 4 instead of i + 3. If you want to round "all the way up," 9 to 16, use i + 7.)

edited Dec 21, 2016 at 22:00

answered Dec 21, 2016 at 21:25

Louis Wasserman

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2 Comments

user7327674 Over a year ago

thanks for your help. what would i use if i wanted to round to a multiple of 225

Louis Wasserman Over a year ago

In general it's just ((i + (n/2)) / n) * n.

Jonny Henly · Accepted Answer · 2016-12-21 21:48:43Z

2

Use the modulo operator (%), which returns the remainder, then add the subtraction of the remainder from 8 to your number.

public static void main(String[] args) { int i = 13; int rem = i % 8 > 0 ? i % 8 : 8; i += 8 - rem; System.out.println(i); }

Outputs: 16

edited Dec 21, 2016 at 21:48

answered Dec 21, 2016 at 21:22

Jonny Henly

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3 Comments

user7327674 Over a year ago

Thanks for the help. however if i input the number 8 it rounds up to 16. how can i get it so the number 8 will stay on 8 and not round up to 16???

Jonny Henly Over a year ago

@user7327674 ahh I forgot to check if i was already a multiple of 8.

Jonny Henly Over a year ago

@user7327674 I updated my answer but it throws a conditional into the mix, your better off using Mureinik's answer or Louis Wasserman's answer.

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