Array creation and usage in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin code?

Consider the following Kotlin code snippet. What will it print when run?

Kotlin

val arr = arrayOf(1, 2, 3, 4)
println(arr[2])

A 3

B 2

C 4

D IndexOutOfBoundsException

💡 Hint

Remember that Kotlin arrays are zero-indexed.

Arrays in Kotlin start at index 0, so arr[2] accesses the third element, which is 3.

❓ Predict Output

intermediate

What does this Kotlin code print?

Look at this Kotlin code. What is the output?

Kotlin

val arr = IntArray(3) { it * 2 }
println(arr.joinToString(","))

A 0,2,4

B 1,2,3

C 0,1,2

D 2,4,6

💡 Hint

The lambda uses the index to calculate each element.

IntArray(3) creates an array of size 3. Each element is set to index * 2, so elements are 0, 2, 4.

❓ Predict Output

advanced

What is the output of this Kotlin code with array mutation?

What will this Kotlin code print?

Kotlin

val arr = arrayOf("a", "b", "c")
arr[1] = "z"
println(arr.joinToString())

A a, b, c

B a, z, c

C a, z, b

D Compilation error

💡 Hint

Arrays in Kotlin are mutable by default.

The second element is changed from 'b' to 'z', so the array prints 'a, z, c'.

❓ Predict Output

advanced

What error does this Kotlin code produce?

What happens when this Kotlin code runs?

Kotlin

val arr = arrayOf(1, 2, 3)
println(arr[3])

A Prints 3

B Prints null

C ArrayIndexOutOfBoundsException

D Compilation error

💡 Hint

Check the valid indices for the array.

The array has indices 0,1,2. Accessing arr[3] is out of bounds and throws an exception.

🧠 Conceptual

expert

How many elements does this Kotlin array contain?

Given this Kotlin code, how many elements are in the array 'arr'?

Kotlin

val arr = Array(5) { i -> i * i }

A 0

B 4

C 6

D 5

💡 Hint

The first argument to Array() is the size.

Array(5) creates an array with 5 elements indexed 0 to 4.