Java Modulo operator

Question

Possible Duplicate:
Floating point inaccuracy examples

When using the modulo operator in java I'm not getting the number I expect to get.

Heres what I'm doing:

double input = 5.59;
System.out.println("Output: " + (input % 2));

I expect to see 1.59 as the result however it is printing out 1.5899999999999999. Any clue as to why this may be?

This comes from floating point inaccuracy, [here is a great SO answer explaining exactly what is happening.](http://stackoverflow.com/a/2100502/874257) — Josiah Hester, Oct 09 '12 at 17:38
Ok, this is a multi multi duplicate (IEEE754, float, etc.). Let us a minute to find it... — Denys Séguret, Oct 09 '12 at 17:39
Another similar question : http://stackoverflow.com/questions/1661273/floating-point-arithmetic-not-producing-exact-results-in-java with answers which may help you — Denys Séguret, Oct 09 '12 at 17:41
Thanks @JosiahHester I'll read up on it. Do oyu know a way I may be able to fix this. I need it for a make change program for my grade 11 programming class. It is supposed to convert a number to exact change. — Matt Langlois, Oct 09 '12 at 17:41

score 5 · Accepted Answer · edited May 23 '17 at 11:43

5

If you want it to round out the number you need to use formatting like this:

double input = 5.59;
System.out.format("Output: %.2f%n", (input % 2));

The "%" tells the formatter to replace itself with the first numeric argument. You can add as many of these as you want.
The ".2" tells the formatter to format the number with two places after the decimal.
The "f" just tells the formatter it is a floating point number.
The "%n" is a new line character appropriate to the platform running the application. You should always use "%n", rather than "\n".

Hope this helps!

edited May 23 '17 at 11:43

Community

answered Oct 09 '12 at 17:40

Josiah Hester

+1 for description provided after edit – exexzian Oct 09 '12 at 17:46
Thanks soo much :P I was trying to get this working for a while now. – Matt Langlois Oct 09 '12 at 17:48

score 1 · Answer 2 · answered Oct 09 '12 at 17:46

1

Its because of precision of Double. You need to format it to achieve your desired output.

double input = 5.59;
System.out.println("Output: " + new DecimalFormat("00.00").format(input % 2));

It will print Output: 1.59

answered Oct 09 '12 at 17:46

2 Answers2