When without argument in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of when without argument with conditions

What is the output of this Kotlin code using when without an argument?

Kotlin

fun main() {
    val x = 15
    val result = when {
        x % 3 == 0 -> "Divisible by 3"
        x % 5 == 0 -> "Divisible by 5"
        else -> "Not divisible by 3 or 5"
    }
    println(result)
}

A Compilation error

B Divisible by 3

C Not divisible by 3 or 5

D Divisible by 5

💡 Hint

Check which condition matches first in the when block.

The when block checks conditions in order. Since 15 is divisible by 3, the first condition is true, so it returns "Divisible by 3".

❓ Predict Output

intermediate

When without argument with Boolean expressions

What will this Kotlin program print?

Kotlin

fun main() {
    val a = 10
    val b = 20
    val output = when {
        a > b -> "a is greater"
        a == b -> "a equals b"
        else -> "a is smaller"
    }
    println(output)
}

A a is smaller

B a equals b

C a is greater

D Runtime exception

💡 Hint

Compare the values of a and b carefully.

Since 10 is less than 20, none of the first two conditions are true, so the else branch runs, printing "a is smaller".

🔧 Debug

advanced

Identify the error in when without argument

What error does this Kotlin code produce?

Kotlin

fun main() {
    val num = 5
    val result = when {
        num > 0 -> "Positive"
        num < 0 -> "Negative"
    }
    println(result)
}

A Prints "Negative"

B Runtime exception: NullPointerException

C Prints "Positive"

D Compilation error: 'when' must be exhaustive

💡 Hint

Check if all possible cases are covered in the when expression.

The when expression without an else branch is not exhaustive. Since num could be zero, the compiler requires an else branch or all cases covered.

🧠 Conceptual

advanced

Behavior of when without argument with multiple true conditions

In Kotlin, when using when without an argument, what happens if multiple conditions are true?

A Only the first true condition's branch executes

B All matching branches execute sequentially

C The last true condition's branch executes

D Compilation error due to ambiguity

💡 Hint

Think about how when expressions work as a control flow.

The when expression checks conditions in order and executes only the first branch whose condition is true.

🚀 Application

expert

Using when without argument to classify numbers

What is the output of this Kotlin program?

Kotlin

fun main() {
    val n = -7
    val classification = when {
        n > 0 && n % 2 == 0 -> "Positive even"
        n > 0 && n % 2 != 0 -> "Positive odd"
        n < 0 && n % 2 == 0 -> "Negative even"
        n < 0 && n % 2 != 0 -> "Negative odd"
        else -> "Zero"
    }
    println(classification)
}

A Negative even

B Positive even

C Negative odd

D Zero

💡 Hint

Check the sign and parity of n carefully.

n is -7, which is negative and odd, so the matching branch is "Negative odd".