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:

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.

val i = "42".toIntOrNull() 

Keep in mind that the result is nullable as the name suggests.

If you actually have a String, call toInt() on it:

val myInt = myString.toInt() 

Are you actually sure it's a String, though? If you're iterating over a single String, you don't get instances of String of length 1 (as you might expect if you're used to another language, ie, Python), but instances of Char, in which case you want to use digitToInt() instead:

val myInt = myChar.digitToInt() 

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 

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".

I use this util function:

fun safeInt(text: String, fallback: Int): Int { return text.toIntOrNull() ?: fallback } 

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.

toInt()

You can call toInt() on a String to turn it into an Integer.

val number_int = str.toInt() 

If it cannot be converted, it will throw a NumberFormatException error.

You could put it in a try-catch block:

try { val strVal = "IamNotanInteger" val intVal = strVal.toInt() println(intVal) } catch (e: NumberFormatException) { println("This String is not convertible.") } 

toIntOrNull()

toIntOrNull() will also convert a String into an Integer, but it will return null instead of throwing an error.

fun main() { val strVal = "246b" val intVal = strVal.toIntOrNull() println(intVal) // null } 

Integer.parseInt()

Here’s how to use the parseInt() method to convert Kotlin String to Int.

fun main() { val strVal = "246" val intVal = Integer.parseInt(strVal) println(intVal) // 246 } 

Non-Decimal System

You can pass a radix into the toInt() and toIntOrNull() methods:

fun main() { val base16String = "3F" val base16Int = base16String.toInt(16) // String Interpolation println("$base16Int") // 63 (If I did the maths correct...) } 

Useful Links

• tutorialkart
• baeldung
• delftstack

add (?) before fun toInt()

val number_int = str?.toInt()

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") } 

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