When with ranges and types in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of when with Int range check

What is the output of this Kotlin code snippet?

Kotlin

fun main() {
    val x = 15
    val result = when (x) {
        in 1..10 -> "Low"
        in 11..20 -> "Medium"
        else -> "High"
    }
    println(result)
}

A Low

B Medium

C High

D Compilation error

💡 Hint

Check which range the value 15 belongs to.

The value 15 falls within the range 11..20, so the when expression returns "Medium".

❓ Predict Output

intermediate

When with type checking

What will be printed by this Kotlin code?

Kotlin

fun main() {
    val obj: Any = "Hello"
    val output = when (obj) {
        is Int -> "Integer"
        is String -> "String"
        else -> "Unknown"
    }
    println(output)
}

A String

B Integer

C Unknown

D Runtime exception

💡 Hint

Check the type of obj at runtime.

The variable obj holds a String, so the when expression matches is String and returns "String".

❓ Predict Output

advanced

When with mixed ranges and types

What is the output of this Kotlin program?

Kotlin

fun main() {
    val input: Any = 25
    val result = when (input) {
        in 1..10 -> "Small number"
        is Int -> "Integer number"
        in 20..30 -> "Medium number"
        else -> "Other"
    }
    println(result)
}

A Integer number

B Medium number

C Small number

D Other

💡 Hint

Remember that when checks branches in order and stops at the first match.

The input 25 is not in 1..10, but is an Int, so the second branch matches and returns "Integer number". The third branch is never reached.

❓ Predict Output

advanced

When with smart casting and type mismatch

What will this Kotlin code print?

Kotlin

fun main() {
    val data: Any = 5.5
    val output = when (data) {
        is Int -> "Int: ${data + 1}"
        is Double -> "Double: ${data + 1}"
        else -> "Unknown type"
    }
    println(output)
}

A Int: 6

B Compilation error

C Double: 6.5

D Unknown type

💡 Hint

Check the actual type of data and how smart casting works.

data is a Double 5.5, so the when branch is Double matches and adds 1 to print "Double: 6.5".

❓ Predict Output

expert

When with complex type and range conditions

What is the output of this Kotlin code?

Kotlin

fun main() {
    val value: Any = 42
    val result = when (value) {
        is Int -> when (value) {
            in 1..10 -> "Small Int"
            in 11..50 -> "Medium Int"
            else -> "Large Int"
        }
        is String -> "String value"
        else -> "Unknown"
    }
    println(result)
}

A Large Int

B Small Int

C Unknown

D Medium Int

💡 Hint

Look carefully at the nested when and the ranges for the Int value.

value is an Int 42, which falls in 11..50, so the nested when returns "Medium Int".