Explicit type declaration in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Kotlin code with explicit type declaration?

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

Kotlin

val number: Int = 10
val text: String = "Hello"
println("$text $number")

A Compilation error

B Hello 10

C 10 Hello

D Hello10

💡 Hint

Look at how the variables are combined inside the println statement.

The variables 'text' and 'number' are combined with a space in between using string interpolation, so the output is 'Hello 10'.

❓ Predict Output

intermediate

What is the type of variable 'result' after this declaration?

Given the Kotlin code below, what is the explicit type of 'result'?

Kotlin

val result: Double = 5 / 2

A Double with value 2.5

B Compilation error

C Int with value 2

D Double with value 2.0

💡 Hint

Remember that 5 and 2 are integers and division between integers behaves differently.

Since 5 and 2 are integers, 5 / 2 performs integer division resulting in 2, then it is converted to Double as 2.0.

🔧 Debug

advanced

Which option causes a compilation error due to explicit type mismatch?

Identify which Kotlin code snippet will cause a compilation error because the assigned value does not match the explicitly declared type.

A val price: Double = 19.99

B val age: Int = 30

C val name: String = 123

D val isActive: Boolean = true

💡 Hint

Check if the value assigned matches the declared type exactly.

Assigning an integer 123 to a variable declared as String causes a compilation error due to type mismatch.

❓ Predict Output

advanced

What is the output of this Kotlin code with explicit nullable type?

Analyze the Kotlin code below and select the correct output.

Kotlin

val message: String? = null
println(message ?: "No message")

A No message

B null

C Compilation error

D Empty string

💡 Hint

The Elvis operator ?: returns the right side if the left side is null.

Since 'message' is null, the Elvis operator returns 'No message'.

🧠 Conceptual

expert

How many variables are explicitly declared as nullable in this Kotlin code?

Count the number of variables explicitly declared with nullable types in the following Kotlin code snippet.

Kotlin

val a: Int? = null
val b: String = "text"
val c: Double? = 3.14
val d: Boolean = true
val e: List<String>? = null

A 3

B 1

C 4

D 2

💡 Hint

Look for the question mark '?' after the type name.

Variables a, c, and e are declared with nullable types (Int?, Double?, List?).