String to number conversion in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin code converting string to integer?

Consider the following Kotlin code snippet that converts a string to an integer. What will be printed?

Kotlin

fun main() {
    val numberString = "1234"
    val number = numberString.toInt()
    println(number + 10)
}

A NumberFormatException

B 1244

C 123410

D 1234

💡 Hint

Remember that toInt() converts the string to an integer number, so arithmetic operations work as expected.

The string "1234" is converted to the integer 1234. Adding 10 results in 1244, which is printed.

❓ Predict Output

intermediate

What happens when converting a non-numeric string to Int in Kotlin?

What will happen when this Kotlin code runs?

Kotlin

fun main() {
    val invalidNumber = "abc"
    val number = invalidNumber.toInt()
    println(number)
}

A NumberFormatException

B 0

C abc

D null

💡 Hint

Think about what happens if you try to convert a string that does not represent a number.

The string "abc" cannot be converted to an integer, so Kotlin throws a NumberFormatException.

❓ Predict Output

advanced

What is the output of safe string to number conversion using toIntOrNull()?

What will this Kotlin program print?

Kotlin

fun main() {
    val input = "42a"
    val number = input.toIntOrNull() ?: -1
    println(number)
}

A 42

B null

C NumberFormatException

D -1

💡 Hint

toIntOrNull() returns null if conversion fails, so the Elvis operator ?: provides a default.

Since "42a" is not a valid integer, toIntOrNull() returns null, so the default -1 is printed.

🧠 Conceptual

advanced

Which Kotlin function converts a string to a Double safely without throwing an exception?

Choose the Kotlin function that converts a string to a Double and returns null if the string is not a valid number.

A toDoubleOrNull()

B toIntOrNull()

C toFloat()

D toDouble()

💡 Hint

Look for the function that ends with 'OrNull' and works with Double type.

toDoubleOrNull() tries to convert the string to Double and returns null if it fails, avoiding exceptions.

❓ Predict Output

expert

What is the output of this Kotlin code converting hexadecimal string to integer?

What will be printed by this Kotlin program?

Kotlin

fun main() {
    val hexString = "1A"
    val number = hexString.toInt(16)
    println(number)
}

A NumberFormatException

B 1A

C 26

D 16

💡 Hint

toInt() can take a radix parameter to convert from different bases like hexadecimal.

The string "1A" in base 16 equals decimal 26, so 26 is printed.