Kotlin Basics

1.		Which of the following is true about extension functions in Kotlin?

Extension functions are a way to add new functionality to existing classes without having to modify their source code.

Extension functions can only be defined for classes that are part of the Kotlin standard library.

Extension functions are not supported in Kotlin.

Extension functions can only be defined for classes that are marked as "open".

2.		Which of the following is a valid identifier in Kotlin?

var

my-variable

123foo

MyClass

3.		What is the syntax for a lambda expression in Kotlin?

{x, y -> x + y}

(x, y) => x + y

[x, y] -> x + y

(x, y) -> {x + y}

4.

What is the output of the following code?

fun main() {
val nullableString: String? = null
val length = nullableString?.length ?: -1
println(length)
}

0

-1

null

This

5.

What is the output of the following code?

fun main() {
val numbers = listOf(1, 2, 3, 4, 5)
val filteredNumbers = numbers.filter { it % 2 == 0 }
println(filteredNumbers)
}

[1, 3, 5]

[2, 4]

[1, 2, 3, 4, 5]

This code will not compile.

6.		What is the difference between a primary constructor and a secondary constructor in Kotlin?

A primary constructor is called before any secondary constructors, while a secondary constructor is called before the primary constructor.

A primary constructor is defined inside the class definition, while a secondary constructor is defined outside the class definition.

A primary constructor takes parameters that are used to initialize properties, while a secondary constructor can have additional logic or functionality.

There is no difference between a primary and a secondary constructor in Kotlin.

7.		What is the difference between "is" and "as" in Kotlin?

is is used for type checking, while "as" is used for casting between types.

is is used for casting between types, while "as" is used for type checking.

is and "as" are interchangeable and can be used interchangeably.

is and "as" are not supported in Kotlin.

8.		What is the Elvis operator in Kotlin?

A type of operator used for bitwise operations.

A type of operator used for arithmetic operations.

A type of operator used for null safety.

A type of operator used for logical operations.

9.		What is Kotlin?

A programming language

A database management system

A web framework

A markup language

10.		What is the primary use case of Kotlin?

Mobile app development

Web development

Database management

Machine learning