Bug In Java Introduction Course

Question

In the module "Control Flow" is anm excercise to code regarding a bill and tip amount.

I entered the code here which is OK:

import java.util.Scanner;

public class Program {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
double billAmount = sc.nextDouble();
double tipAmount = billAmount/100*15;
System.out.println(tipAmount);

}
}

But one of the four tests (Test 3) fail.
It shows me that my output is 232.20000000000002 and the expected output is 232.2.

I tried in mobile app (OS) and WIndows Desktop and receive this error on both environments.

Answer 1

Attila Kipfer ,

billAmount/100*15
billAmount*15/100

should mathematically give the same result. but in reality these operations can give *different results* due to floating-point precision issues and integer division behavior.

> see also:
https://softwareengineering.stackexchange.com/questions/101163/what-causes-floating-point-rounding-errors?utm_source=perplexity

Answer 2

Try this.
double tipAmount = billAmount * 15 / 100;

I'm not sure why, but divided by 100 always works better than by 15.