How to find if a number or fraction is integer in java?

Question

How to find if a number or fraction is an integer in Java?

I did some research before but struggle to apply them. I want to do something like this:

if (x is int){
   //commands
}

How do you find if a number is an integer or a fraction without Java? — Elliott Frisch, Feb 19 '18 at 17:20
A fraction is an integer if its denominator divides the numerator: `num % den == 0`. — Andy Turner, Feb 19 '18 at 17:21
You're always guaranteed the type of a primitive. It gets slightly murkier with `Number` since any primitive numeral can unbox to `Number`, but it largely depends on how you're getting the value in the first place. Is it a primitive or an object? — Makoto, Feb 19 '18 at 17:21
If a double is between -2^53 and 2^53-1, cast it to long and back to double, see if the value is the same as the original. Any finite value outside that range will always be an integer, because there is insufficient precision for it to be otherwise. — Andy Turner, Feb 19 '18 at 17:23
Wait - do you want the mixed number variation of the double? That's...a display concern and absolutely has nothing to do with the actual storage of the number itself. You'd have to do some custom display work to get that to work out. — Makoto, Feb 19 '18 at 17:25

score 1 · Accepted Answer · answered Feb 19 '18 at 17:27

1

You should use something like this:

if((x%1)==0){
//do stuff
}

This checks to see if the decimal part of the number is zero.

answered Feb 19 '18 at 17:27

TMcSquared

how do you do the same with infinite digit decimal, like 10/3 – Skill HHY Feb 19 '18 at 17:31
when I do double c=10/3; if(c%1==0){ System.out.print(c); } – Skill HHY Feb 19 '18 at 17:32
It prints 3.000 – Skill HHY Feb 19 '18 at 17:32
@SkillHHY That's an issue with your division. `10/3` is integer division. Try `10.0/3.0`. Or only one (`10.0/3` or `10/3.0`) or cast (`((double)10)/3`). See https://stackoverflow.com/questions/4685450/why-is-the-result-of-1-3-0 – AntonH Feb 19 '18 at 17:40
Thank you very much – Skill HHY Feb 19 '18 at 17:42

1 Answers1