Function declaration syntax in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple function call

What is the output of this Kotlin code?

Kotlin

fun greet(name: String): String {
    return "Hello, $name!"
}

fun main() {
    println(greet("Alice"))
}

A Hello, Alice!

B greet(Alice)

C Hello, name!

D Error: Missing return statement

💡 Hint

Look at how the function returns a greeting string using the input name.

The function greet takes a string parameter and returns a greeting message. Calling greet("Alice") returns "Hello, Alice!" which is printed.

❓ Predict Output

intermediate

Function with default parameter value

What will this Kotlin program print?

Kotlin

fun multiply(x: Int, y: Int = 2): Int {
    return x * y
}

fun main() {
    println(multiply(5))
}

A 10

B 7

C Error: Missing argument for y

D 25

💡 Hint

Check the default value of parameter y.

The function multiply has a default value of 2 for y. Calling multiply(5) uses y=2, so 5*2=10 is printed.

❓ Predict Output

advanced

Single-expression function output

What does this Kotlin code print?

Kotlin

fun square(n: Int) = n * n

fun main() {
    println(square(4))
}

A n * n

B 4

C Error: Missing return type

D 16

💡 Hint

Single-expression functions return the expression value automatically.

The function square returns n multiplied by n. For input 4, it returns 16.

❓ Predict Output

advanced

Function with no return value

What is the output of this Kotlin program?

Kotlin

fun printMessage(message: String): Unit {
    println("Message: $message")
}

fun main() {
    printMessage("Hi there")
}

A Error: Function must return a value

B Unit

C Message: Hi there

D Hi there

💡 Hint

Unit means the function returns no meaningful value but can print output.

The function prints the message with prefix "Message:". The output is that line.

❓ Predict Output

expert

Function with named arguments and default values

What will this Kotlin code print?

Kotlin

fun formatText(text: String, prefix: String = "", suffix: String = "") = "$prefix$text$suffix"

fun main() {
    println(formatText(suffix = "!", text = "Hello"))
}

A !Hello

B Hello!

C Hello

D Error: Named arguments must be in order

💡 Hint

Named arguments can be passed in any order in Kotlin.

The function concatenates prefix, text, and suffix. Here prefix is default empty, suffix is "!", text is "Hello", so output is "Hello!".