How to use the toIntOrNull() method of String in Kotlin

The toIntOrNull() method will parse the string as an integer number and returns it. If the string is not a valid number, then null is returned.

Syntax

fun String.toIntOrNull(): Int?

Parameter

This method doesn’t take any argument.

Return value

This method returns the Int value if the string is a valid number. Otherwise, null is returned.

Code

The below method demonstrates how to use the toIntOrNull() method.

fun main() {
    val intNum="10"
    val invalidNum = "ab";
    val floatingNum = "10.3"
    
    println("'${intNum}'.toIntOrNull -> ${intNum.toIntOrNull()}")
    println("'${invalidNum}'.toIntOrNull -> ${invalidNum.toIntOrNull()}")
    println("'${floatingNum}'.toIntOrNull -> ${floatingNum.toIntOrNull()}")
}

Explanation

In the above code:

  • Lines 2-4: We created three string variables.

  • Line 6: We used the toIntOrNull method to convert the intNum string to an integer value. The string is a valid integer value, so it is parsed to the Int value and returned.

  • Lines 7 & 8: We used the toIntOrNull method to convert the invalidNum and floatingNum strings to an integer value. Both of the strings cannot be parsed to an Int value, so null is returned.

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