AAD AAD Kotlin & Programming Fundamentals 2

Question 1

What is the key difference between `val` and `var` in Kotlin?

Accepted Answer

`val` is a read-only reference that cannot be reassigned; `var` is mutable and can be reassigned

Answer

val declares a read-only reference (like final in Java) that cannot be reassigned after initialization, while var declares a mutable variable that can be reassigned.

Question 2

What is an extension function in Kotlin?

Accepted Answer

A function that adds new functionality to an existing class without modifying its source code

Answer

An extension function lets you add new functions to an existing class without inheriting from it or modifying its source, using the syntax fun ClassName.newFunction().

Question 3

What does the `suspend` keyword indicate in Kotlin?

Accepted Answer

The function can be paused and resumed within a coroutine without blocking the calling thread

Answer

A suspend function can suspend coroutine execution at a specific point without blocking the thread, and can only be called from a coroutine or another suspend function.

Question 4

What is a sealed class in Kotlin?

Accepted Answer

A class hierarchy where all subclasses are defined in the same file, enabling exhaustive when expressions

Answer

A sealed class restricts class hierarchies so all direct subclasses must be defined in the same file, allowing exhaustive when expressions without an else branch.

Question 5

What is the `when` expression in Kotlin?

Accepted Answer

A replacement for Java's switch statement that matches a value against multiple branches

Answer

Kotlin's when expression matches a value against a series of branches and returns the value of the matching branch, serving as a more powerful switch statement.

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AAD AAD Kotlin & Programming Fundamentals 2