Dividing two integers in Java gives me 0 or 100?

Question

I'm trying to divide two integers and multiply by 100 but it keeps giving only 0 or 100. Can someone help me?

    int x= (a/b)*100;

if a was 500 and b was 1000 it would give me 0. The only time it will give me 100 is if a>=b. How can I fix this?

Thanks

Please explain the expected result. – Vincent Cantin Dec 29 '11 at 16:52 — Vincent Cantin, Dec 29 '11 at 16:52

score 47 · Accepted Answer · edited Dec 21 '17 at 17:39

47

What you could do is force it to divide a and b as doubles thus:

int x = (int) (((double) a / (double) b) * 100);

edited Dec 21 '17 at 17:39

edwoollard

answered Dec 29 '11 at 15:42

ridecar2

This one is missing a cast to `int`. Otherwise it will not compile. – Howard Dec 29 '11 at 15:44
Please accept as answer as it will raise this answer to the top and help others, thanks. – ridecar2 Dec 29 '11 at 15:47

score 10 · Answer 2 · answered Dec 29 '11 at 15:41

10

Integer division has no fractions, so 500 / 1000 = 0.5 (that is no integer!) which gets truncated to integer 0. You probably want

int x = a * 100 / b;

answered Dec 29 '11 at 15:41

Simon Urbanek

score 6 · Answer 3 · answered Dec 29 '11 at 15:40

6

This sounds like you are not correctly typing your variables; two integer divisions result in an integer, not a float or double. For example:

(int)3 / (int)5 = 0
(float)3 / (float)5 = 0.6

answered Dec 29 '11 at 15:40

Tejs

score 3 · Answer 4 · answered Dec 29 '11 at 15:41

3

Try this:

int x = a * 100 / b;

The idea is, you are first doing a / b, and because it's an integer operation, it'll round the result to 0. Doing a * 100 first should fix it.

answered Dec 29 '11 at 15:41

cambraca

score 0 · Answer 5 · answered Feb 27 '20 at 01:30

0

Simplest, most effective way I found:

double x = (double) a / (double) b

answered Feb 27 '20 at 01:30

Coleman B

correct answer, though I'd think it even more helpful to explain how integer division caused this issue – Paul Degnan Feb 27 '20 at 03:04

5 Answers5