Why is Math.ceil not rounding upwards?

Question

I have the following code:

int total = 6;
int perPage = 5;
double pages = total/perPage;
double ceilPages = Math.ceil(pages);
out.println(ceilPages);

Which outputs 1.0.

I thought it should output 2.0 because the result of total/perPage is 1.2.

Why is it not rounding upwards to 2.0?

You are performing an integer division not a floating point one. — Sirko, Jun 05 '14 at 14:10
`int ceilPages = (total + perPage - 1) / perPage;` is neater. — Joop Eggen, Jun 05 '14 at 14:13
Did you try printing `pages` to see what value you passed into `Math.ceil()`? That would have immediately told you the problem was not with `Math.ceil()`. — dimo414, Jun 05 '14 at 14:41
possible duplicate of [How to Round Up The Result Of Integer Division](http://stackoverflow.com/questions/17944/how-to-round-up-the-result-of-integer-division) — Ali, Jun 05 '14 at 14:42
(int)Math.ceil(3/2.0) will give answer 2 (int)Math.ceil(3/2) will give answer 1 In order to get the float value, you need to cast (or add .0) to one of the arguments — Shyam Sunder, Mar 08 '18 at 16:34

score 26 · Accepted Answer · answered Jun 05 '14 at 14:11

26

you are casting an the result of integer division to a double.

You need to cast each part of the division to double BEFORE the result.

double pages = (double)total/(double)perPage;

The rest should work

answered Jun 05 '14 at 14:11

Adam Yost

8

Not each part. Casting the first one should be sufficient. – Isaac Jun 05 '14 at 14:12

score 3 · Answer 2 · answered Mar 08 '18 at 16:32

3

(int)Math.ceil(3/2.0) will give answer 2

(int)Math.ceil(3/2) will give answer 1

In order to get the float value, you need to cast (or add .0) to one of the arguments

answered Mar 08 '18 at 16:32

Shyam Sunder

score 0 · Answer 3 · answered Nov 24 '17 at 06:34

0

double pages = Math.ceil((double)total/perPage);

answered Nov 24 '17 at 06:34

Chandan Kumar

3 Answers3