Dividing two integers and rounding up result to nearest integer

Question

I have two int numbers a, b always >= 0. I want to divide a by b and return the rounded up percentage to the nearest integer.

Example: 18/38 should return 47 and 13/38 should return 34.

How can I accomplish this?

I tried the following but it didn't work

c = Math.round(a/b) * 100;

a/b is an integer division. You need to cast at least one of the operands to a double to have a double division. — JB Nizet, May 07 '19 at 17:43

score 3 · Accepted Answer · answered May 07 '19 at 17:43

3

Since a and b are integers, a/b will use integer division, and only return the "whole" part of the result. Instead, you should multiply a by 100.0 (note the .0, which makes it a double literal!) to use floating-point division, and then ceil the result, and truncate it to an int:

c = (int) Math.ceil(100.0 * a / b);

answered May 07 '19 at 17:43

Mureinik

252,575
45
248
283

`c = (int) Math.round(100.0 * a / b);` will give 47 which is intended – Talha May 07 '19 at 17:50
Thank you for your answer! I'm getting 18/38=45 and 13/38=35 for some reason though? – BigMon May 07 '19 at 17:51
@BigMon the text of your question and the example you gave contradict each other. E.g., 13/38 is roughly 34.21% - if you want to round it up like the text says you'll get 35, which the code returns; If you want to get 34 that would be rounding down, and you should use `floor` instead of `ceil` - or, of course, you could just use `round` to get the nearest integer. – Mureinik May 07 '19 at 17:55
@Mureinik that's my bad, I changed ceil to round as you said and it seems to work as I want it. – BigMon May 07 '19 at 18:00

Shivam Mohan · Answer 2 · 2019-05-07T17:59:18.437

0

c = (int) Math.round(100.0 * a / b);

This should give desired result.

edited May 07 '19 at 17:59

answered May 07 '19 at 17:55

Shivam Mohan

402
2
13

`Math.floor` always rounds down better to use `Math.round`. – Talha May 07 '19 at 17:57
Correct, my bad. – Shivam Mohan May 07 '19 at 17:59

score 0 · Answer 3 · answered May 07 '19 at 17:55

0

You need to do follow things to get the result

Double res= Double.valueof(a/b);
DecimalFormat decimalFormat = new DecimalFormat("#.00");
String num= decimalFormat.format(res);
Int finalResult = Integer.valueof(num)*100;

Thanks

answered May 07 '19 at 17:55

Ajay Kumar Sharma

60
5

score 0 · Answer 4 · answered May 07 '19 at 17:55

public static void main(String[] args){
int a=18,b=38,c=0;
c = (int) Math.round(100.0 * a / b);    
System.out.println(c);
}

As @Mureinik said that a and b are integers,they will use integer division. you should multiply 100 by a like above. and keep using .round instead of .ceil inorder to get 47 as output which is intended .ceil will give you 48 as output.

Dividing two integers and rounding up result to nearest integer

4 Answers4