Kotlin

Question 1

What is kotlin

Answer 1

Is a modern language that runs on the JVM

Question 2

What are the differences between Kotlin and Java

Answer 2

Null safety, concise syntax, extension functions, data classes, coroutines

Question 3

Explain null safety in Kotlin

Answer 3

Kotlin prevents NullPointerExceptions by requiring explicit null checks

Question 4

Kotlin types

Answer 4

Int, Long, Float, Double, Boolean, Char, String

Question 5

What’s the difference between “val” and “var”

Answer 5

Val creates immutable variables, while var creates mutable variables

Question 6

Explain the concept of type inference

Answer 6

The compiles automatically infers the type of a variable based on its initialization value

Question 7

What are higher-order functions in Kotlin

Answer 7

Functions that take other functions as parameters, or returns functions as results

Question 8

What is a lambda expression in Kotlin

Answer 8

A function literal that can be passed as an argument or assigned to a variable
Val sayHello = { println(“Hello world”) }
Val add = { x: Int, y: Int -> x + y }

Question 9

Explain the concept of extension functions in Kotlin

Answer 9

Add new functionality to existing classes without modifying their source code
class ExClass() {some_code_here}

fun ExClass.extensionFunction(parameter: Int): Int {
return parameter
}

val exClass = ExClass()
exClass.extensionFunction(5)

Question 10

What are data classes in Kotlin

Answer 10

Classes that hold data, automatically generating equals(), hashCode(), toString(), and copy() methods

Question 11

What is the difference between a primary and a secondary constructor

Answer 11

Primary constructor is defined with the class name, while secondary constructors delegate to the primary constructor

class Person(thisIsThePrimaryConstructor){}

Class Student {
// Some properties
constructor(thisIsSecondaryConstructor){
This.property = propertyInTheConstructor
}
}

Question 12

What is the purpose of companion objects in Kotlin

Answer 12

Crate static-like members for a class

class ClassName {
companion object {
const val propertyName= some_value
fun funName(){function_code}
}
}

val property = ClassName.propertyName
ClassName.funName()

Question 13

Explain the concept of sealed classes in Kotlin

Answer 13

Restricted class hierarchy with subclasses known at compile time

Question 14

What is the difference between a list and a mutable list in Kotlin

Answer 14

List is immutable, the mutable list can be modified

Question 15

What is the difference between a map and a set in kotlin

Answer 15

A map stores key-value pairs, while sets stores unique elements

Question 16

Explain the concept of generics in Kotlin

Answer 16

Create type-safe code by using placeholders for specific types

Class ClassName<GenericTypeName>(private val value: GenericTypeName){}</GenericTypeName>

Question 17

What is the purpose of the “when” expression in kotlin

Answer 17

A concise way to perform conditional checks
when(x) {
1 -> print(“x == 1”)
2 -> print(“x == 2”)
else -> {
print(“x is neither 1 nor 2”)
}
}

Question 18

What is the purpose of ?. operator in Kotlin

Answer 18

Safe call operator to prevent NullPointerExceptions

Question 19

What is the purpose of the !! operator in Kotlin

Answer 19

Non-null assertion operator, use with caution

Question 20

Explain the concept of coroutines in Kotlin

Answer 20

Asynchronous programming model for writing non-blocking code