How to convert String to Int in Kotlin? - kotlin

Question

I am working on a console application in Kotlin where I accept multiple arguments in main() function
fun main(args: Array<String>) {
// validation & String to Integer conversion
}
I want to check whether the String is a valid integer and convert the same or else I have to throw some exception.
How can I resolve this?

Answer 1

You could call toInt() on your String instances:
fun main(args: Array<String>) {
for (str in args) {
try {
val parsedInt = str.toInt()
println("The parsed int is $parsedInt")
} catch (nfe: NumberFormatException) {
// not a valid int
}
}
}
Or toIntOrNull() as an alternative:
for (str in args) {
val parsedInt = str.toIntOrNull()
if (parsedInt != null) {
println("The parsed int is $parsedInt")
} else {
// not a valid int
}
}
If you don't care about the invalid values, then you could combine toIntOrNull() with the safe call operator and a scope function, for example:
for (str in args) {
str.toIntOrNull()?.let {
println("The parsed int is $it")
}
}

Answer 2

Actually, there are several ways:
Given:
// aString is the string that we want to convert to number
// defaultValue is the backup value (integer) we'll have in case of conversion failed
var aString: String = "aString"
var defaultValue : Int = defaultValue
Then we have:
Operation
Successful operation
Unsuccessful Operation
aString.toInt()
Numeric value
NumberFormatException
aString.toIntOrNull()
Numeric value
null
aString.toIntOrNull() ?: defaultValue
Numeric value
defaultValue
If aString is a valid integer, then we will get is numeric value, else, based on the function used, see a result in column Unsuccessful Operation.

Answer 3

val i = "42".toIntOrNull()
Keep in mind that the result is nullable as the name suggests.

Answer 4

As suggested above, use toIntOrNull().
Parses the string as an [Int] number and returns the result
or null if the string is not a valid representation of a number.
val a = "11".toIntOrNull() // 11
val b = "-11".toIntOrNull() // -11
val c = "11.7".toIntOrNull() // null
val d = "11.0".toIntOrNull() // null
val e = "abc".toIntOrNull() // null
val f = null?.toIntOrNull() // null

Answer 5

I use this util function:
fun safeInt(text: String, fallback: Int): Int {
return text.toIntOrNull() ?: fallback
}

Answer 6

In Kotlin:
Simply do that
val abc = try {stringNumber.toInt()}catch (e:Exception){0}
In catch block you can set default value for any case string is not converted to "Int".

Answer 7

string_name.toString().toInt()
converts string_name to String and then the resulting String is converted to int.

Answer 8

i would go with something like this.
import java.util.*
fun String?.asOptionalInt() = Optional.ofNullable(this).map { it.toIntOrNull() }
fun main(args: Array<String>) {
val intArgs = args.map {
it.asOptionalInt().orElseThrow {
IllegalArgumentException("cannot parse to int $it")
}
}
println(intArgs)
}
this is quite a nice way to do this, without introducing unsafe nullable values.

Answer 9

add (?) before fun toInt()
val number_int = str?.toInt()

Answer 10

You can Direct Change by using readLine()!!.toInt()
Example:
fun main(){
print("Enter the radius = ")
var r1 = readLine()!!.toInt()
var area = (3.14*r1*r1)
println("Area is $area")
}

Answer 11

fun getIntValueFromString(value : String): Int {
var returnValue = ""
value.forEach {
val item = it.toString().toIntOrNull()
if(item is Int){
returnValue += item.toString()
}
}
return returnValue.toInt()
}