How to to check fractional part on double?

Question

i would like to know how to get the fractional part of a double. Im trying the following code:

double auxValMin= Double.parseDouble("5.3");
double auxDecimal= auxValMin-floor(auxValMin);
System.out.println(auxDecimal); //I get 0.2999999999999998 instead of 0.3

How can i fix the "0.2999999999999998"?

You should use BigDecimal in this case. See here: http://stackoverflow.com/questions/3413448/double-vs-bigdecimal — Przemek Nowak, Dec 21 '14 at 09:02
If you only want to display the decimal part, use `split` and print it as a String. — Maroun, Dec 21 '14 at 09:03
@BoxEdition I think you should accept the answer if it answers your query. :) — Pankaj Singhal, Dec 22 '14 at 17:18

score 1 · Accepted Answer · edited May 23 '17 at 10:26

double has more accuracy of precision that float but still has rounding errors. You have to round any answer you get to have a sane output.

If this is not desireable you can use BigDecimal which does not have rounding errors, but has its own headaches IMHO.

The default Float.toString() uses minimal rounding, but often its not enough.

System.out.println("With no rounding");
double n = 5.3d;
System.out.println("n= "+new BigDecimal(n));
double expected = 0.3d;
System.out.println("expected= "+new BigDecimal(expected));

System.out.println("n % 1= "+new BigDecimal(n % 1));
System.out.println("n - Math.floor(n) = "+new BigDecimal(n - Math.floor(n)));
System.out.println("n - (int)n= "+new BigDecimal(n - (int)n));

System.out.println("With rounding");
System.out.printf("n %% 1= %.2f%n", n % 1);
System.out.printf("n - Math.floor(n) = %.2f%n", n - Math.floor(n));
System.out.printf("n - (int)n= %.2f%n", n - (int)n);

Prints

With no rounding
n= 5.29999999999999982236431605997495353221893310546875
expected= 0.299999999999999988897769753748434595763683319091796875
n % 1= 0.29999999999999982236431605997495353221893310546875
n - Math.floor(n) = 0.29999999999999982236431605997495353221893310546875
n - (int)n= 0.29999999999999982236431605997495353221893310546875 
With rounding
n % 1= 0.30
n - Math.floor(n) = 0.30
n - (int)n= 0.30

A bit of a googling might have helped : https://stackoverflow.com/a/5017110/820410

score 1 · Answer 2 · answered Dec 21 '14 at 09:33

1

Now a day BigDecimal you will get Java.Please read and learn it about BigDecimal

 BigDecimal value=new BigDecimal("5.36777777");
    System.out.println( value.round(new MathContext(2, RoundingMode.CEILING)));

answered Dec 21 '14 at 09:33

Abhishek Mishra

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How to to check fractional part on double?

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