Main function as entry point in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin program?

Consider this Kotlin program with a main function. What will it print when run?

Kotlin

fun main() {
    println("Hello, Kotlin!")
}

A No output

B hello, kotlin!

C Hello, Kotlin!

D Compilation error

💡 Hint

The main function is the starting point of a Kotlin program.

The main function runs first and prints the exact string inside println, preserving case.

❓ Predict Output

intermediate

What happens if main has parameters but is called without arguments?

Look at this Kotlin main function with parameters. What will happen if you run this program without passing any command-line arguments?

Kotlin

fun main(args: Array<String>) {
    println("Arguments count: ${args.size}")
}

A Compilation error

B Arguments count: 0

C Runtime error

D Arguments count: null

💡 Hint

The args array is always passed, even if empty.

The args array is empty if no command-line arguments are given, so size is 0.

❓ Predict Output

advanced

What is the output of this Kotlin program with multiple main functions?

This Kotlin file has two main functions. Which one will run and what will be printed?

Kotlin

fun main() {
    println("First main")
}

fun main(args: Array<String>) {
    println("Second main")
}

A First main

B No output

C Compilation error due to duplicate main

D Second main

💡 Hint

Kotlin prefers main with parameters as entry point.

When running from command line, Kotlin uses main with Array parameter if present.

❓ Predict Output

advanced

What error does this Kotlin program produce?

This Kotlin program tries to define main with a wrong signature. What error will it cause?

Kotlin

fun main(args: String) {
    println(args)
}

A Runtime error: main function must have Array<String> parameter or no parameters

B Runtime error: wrong argument type

C Prints the string argument

D No output

💡 Hint

Main function signature must be exact.

Kotlin requires main to have either no parameters or Array parameter; String alone is invalid.

🧠 Conceptual

expert

How many main functions can a Kotlin program have without causing errors?

Select the correct statement about the number of main functions allowed in a Kotlin program.

A Two main functions are allowed: one with no parameters and one with Array<String> parameter

B Only one main function is allowed, with Array<String> parameter

C Only one main function is allowed, with no parameters

D Multiple main functions with any signatures are allowed

💡 Hint

Kotlin supports main function overloading with specific signatures.

Kotlin allows exactly two main functions: one with no parameters and one with Array parameter, to support different entry points.