Avoiding rounding when doing calculation

Question

I've a piece of Java code from here which converts a number to words, it's working fine but the fraction is always 1 less than it should be, ex. 122.11 is printed 122.10.

Here is piece of code which is doing the calculation. How can I solve this issue?

    String phrase = "122.11" ;
    Float num = new Float( phrase ) ;
    int dollars = (int)Math.floor( num ) ;
    int cent = (int)Math.floor( ( num - dollars ) * 100.0f ) ;

Could you please post the whole code of your's because this code is working fine and `num` contains two decimal digits — Ashishkumar Singh, Mar 28 '19 at 11:34
When I see `dollars` I would immediately use `BigDecimal` instead of `Float`. — Michu93, Mar 28 '19 at 11:38
Please edit your code, to display the complete problem. the present code gives you 122 and 12 as expected — VSB, Mar 28 '19 at 12:29
the full code could be found here https://stackoverflow.com/questions/3911966/how-to-convert-number-to-words-in-java — JAVADEV, Mar 28 '19 at 13:26

One Man Crew · Answer 1 · 2019-03-28T14:38:51.813

0

String phrase = " 555243.22" ;
Double num = new Double( phrase ) ;
double dollarsAsDouble =  Math.floor( num ) ;
double val=num - dollarsAsDouble+0.005;
int cent = (int)Math.floor(val * 100.0f ) ;
int dollars=(int) dollarsAsDouble;
System.out.println(cent);//555234
System.out.println(dollars);//22

or:

String phrase = "122.12" ;
String[] val=phrase.split("\\.");
int dollars=new Integer(val[0]);
int cent=0;
if(val.length>1)
    cent=new Integer(val[1]);

System.out.println(cent);
System.out.println(dollars);

or:

String phrase = "555243.22" ;
BigDecimal num = new BigDecimal(phrase);
num.setScale(2, BigDecimal.ROUND_HALF_UP);
BigDecimal result = num.subtract(new BigDecimal(num.longValue()));
System.out.println((int)(result.doubleValue()*100.0)); // 22
System.out.println(num.intValue());//555243

edited Mar 28 '19 at 14:38

answered Mar 28 '19 at 11:37

One Man Crew

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First solution is not ok when the amount get bigger like 555,243.22 then the .22 is printed .25 , second solution is working fine – JAVADEV Mar 28 '19 at 13:24
@JAVADEV i fixed the first solution to work with bigger numbers.you need to use Double type and not Float type! – One Man Crew Mar 28 '19 at 14:07
@JAVADEV I added third solution with BigDecimal – One Man Crew Mar 28 '19 at 14:40

Igor F. · Answer 2 · 2019-03-28T12:46:33.447

0

0.11 cannot be represented exactly in the floating point arithmetic, and ends up being 0.1099999something internally (0.10999999999999943, at least on my machine, but that should be universal). Multiply by 100 and floor it, and you get 10. You can easily circumvent this by rounding the 100-fold number, instead of flooring it, simply by adding 0.5 to the number you want to round. And, you can skip the Math.floor(), as casting the number to int already does what you want:

int cent = (int)( ( num - dollars ) * 100.0f + 0.5f) ;

edited Mar 28 '19 at 12:46

answered Mar 28 '19 at 11:40

Igor F.

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this solution is giving wrong results when the number gets bigger, ex. 543,122.22 restult fraction is .25 – JAVADEV Mar 28 '19 at 13:15
Sure, but that follows from your choice of using `float`s. They give you only 6-7 significant decimal digits (24 binary digits, to be exact). If you used `double`, which is the default FP format in Java, you'd have 15 significant digits. If that isn't enough, e.g. because you are calculating the federal budget of the USA, I concur with other posters and suggest you use `BigDecimal`. – Igor F. Mar 28 '19 at 13:35

Avoiding rounding when doing calculation

2 Answers2