Kotlin: How do i check if a number has decimal points (modulus solution doesn't work)

Question

I'm new to Kotlin and came from JS. I am currently making a calculator app and am working on the '%' operator. I need to find out if the output of the 'current input * 0.01' is a whole number or with decimal points. Usually, I would use

num % 1 !== 0

but it does not work in Kotlin and gives me the error "!= operator cannot be applied to Double or Int". It is the same for Strings or Characters. My Kotlin code is below, hope someone can help! Thanks!

val percentResult: Double() = result.toDouble() * 0.01
  if(percentResult % 1 != 0) {
   result = (NumberFormat.getInstance().format(percentResult)).toString()
  } else {
   result = percentResult.toInt().toString()
  }

check https://stackoverflow.com/questions/10496616/how-to-remove-the-decimal-part-from-a-float-number-that-contains-0-in-java — Atif AbbAsi, Feb 23 '21 at 18:23

score 15 · Answer 1 · answered Apr 29 '20 at 08:18

15

In Kotlin you can use the "rem" function:

if (number.rem(1).equals(0.0))

answered Apr 29 '20 at 08:18

Geeky bean

475
6
21

jrtapsell · Accepted Answer · 2017-10-16T09:43:44.643

Equivalent code

The 0 is an int, so you need to explicitly say you want a double like this:

fun factor100(n: Number) = n.toDouble() % 100.0 == 0.0

Why this probably is not what you want

For double values this may not work correctly, due to floating point errors, so you will want to check if the difference is smaller than some small amount.

An example of how this is broken is this:

fun main(args: Array<String>) {
    var x = 0.3 - 0.2         // 0.1 (ish)
    x *= 1000                 // 100 (ish)
    println(factor100(x))     // False
}

fun factor100(n: Number) = n.toDouble() % 100.0 == 0.0

score 7 · Answer 3 · answered Nov 29 '19 at 13:37

7

See https://stackoverflow.com/a/45422616/2914140.

num % 1.0 != 0.0 // But better compare with a small constant like 1e-8.

For currency:

num.absoluteValue % 1.0 >= 0.005 (or other small constant).

answered Nov 29 '19 at 13:37

CoolMind

26,736
15
188
224

score -1 · Answer 4 · answered Jul 27 '18 at 17:36

I don't know if im just lazy searching how to do this with core functions or there are no solutions about it. So i solved it doing this:

fun Double?.checkDecimals(decimals: Int): Boolean {
    if (this == null) return false
    val comparator = 10.0.pow(decimals)
    val doubleTimesComparator = (this * comparator)
    val integerUnit = doubleTimesComparator.toInt()
    return doubleTimesComparator == integerUnit.toDouble()
}

*android

Kotlin: How do i check if a number has decimal points (modulus solution doesn't work)

4 Answers4

Equivalent code

Why this probably is not what you want