Kotlin REPL and script mode - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of variable reassignment in Kotlin REPL

What is the output of the following Kotlin REPL session?

Kotlin

var x = 5
x = x + 3
println(x)

A 8

B 5

C Compilation error

D Runtime exception

💡 Hint

Remember that 'var' allows reassignment in Kotlin.

The variable x is initially 5, then increased by 3, so the output is 8.

❓ Predict Output

intermediate

Script mode output with top-level function

What will be printed when running this Kotlin script file?

Kotlin

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

A No output

B greet

C Compilation error: function must be inside a class

D Hello, Alice!

💡 Hint

Kotlin scripts allow top-level functions and execute statements immediately.

The script defines a function and calls it immediately, printing the greeting.

❓ Predict Output

advanced

REPL session with shadowing and type inference

What is the output of this Kotlin REPL session?

Kotlin

val x = 10
val x = "Ten"
println(x)

A Ten

B 10

C Compilation error: val x already defined

D Runtime exception

💡 Hint

In Kotlin REPL, you can shadow previous variables by redeclaring them.

The second declaration shadows the first, so x is a String "Ten" when printed.

❓ Predict Output

advanced

Script mode with top-level statements and variable scope

What will be the output of this Kotlin script?

Kotlin

val a = 5
fun printA() {
    val a = 10
    println(a)
}
printA()
println(a)

A Compilation error: variable a redeclared

B

5
10

C

10
5

D

10
10

💡 Hint

Local variables inside functions shadow outer variables.

Inside printA(), local a=10 is printed. Outside, top-level a=5 is printed.

🧠 Conceptual

expert

Difference between Kotlin REPL and script mode execution

Which statement correctly describes a key difference between Kotlin REPL and Kotlin script mode?

A Kotlin REPL does not support variable reassignment, but script mode does.

B Kotlin REPL executes code line-by-line interactively, while script mode runs the entire file as a single unit.

C Kotlin REPL compiles to JVM bytecode, but script mode runs only interpreted code.

D Kotlin REPL requires all code inside functions, but script mode allows top-level statements.

💡 Hint

Think about how REPL and scripts handle code execution timing.

REPL executes each entered line immediately and interactively; scripts run the whole file at once.