Kotlin
Kotlin is a modern, statically-typed programming language developed by JetBrains. It is fully interoperable with Java and widely used for Android app development, server-side applications, and scripting. In this chapter, we will explore Kotlin syntax, variables, data types, functions, control flow, classes, objects, and a final example.
Introduction to Kotlin
Kotlin files use the .kt extension. Programs start with a main function. Kotlin is concise, expressive, and supports functional programming alongside object-oriented programming.
Variables and Data Types
Kotlin supports immutable variables (val) and mutable variables (var). Common data types include Int, Double, Float, Boolean, Char, String.
val name: String = "Riya"<br>
var age: Int = 14<br>
val height: Double = 5.6<br>
var isStudent: Boolean = true<br>
val grade: Char = 'A'<br>
>Functions
Functions are defined using fun. Kotlin supports default parameters and expression body functions.
fun greet(name: String) {<br>
println("Hello, $name!")<br>
}<br>
fun sum(a: Int, b: Int): Int = a + b<br>
>Control Flow
Kotlin supports if, else, when statements for conditional execution.
Loops
Repetition is supported with for, while, and do-while loops.
Classes and Objects
Classes are defined using class. Objects are instances created using the constructor or init block.
Final Example — Collatz Sequence
This example demonstrates the Collatz sequence using Kotlin. Save as Collatz.kt.
fun main() {<br>
print("Enter a number: ")<br>
var n = readLine()!!.toInt()<br>
while (n != 1) {<br>
print("$n ")<br>
if (n % 2 == 0) n /= 2<br>
else n = 3*n + 1<br>
}<br>
println("1")<br>
}<br>
>MCQs
1. Which keyword is used for defining a variable that cannot be reassigned?
(a) var
(b) val
(c) const
(d) let
► (b) val
2. Which keyword defines a function in Kotlin?
(a) function
(b) def
(c) fun
(d) lambda
► (c) fun
3. What is the correct way to declare a string in Kotlin?
(a) var name = 'Riya'
(b) var name = "Riya"
(c) var name = Riya
(d) var name = `Riya`
► (b) var name = "Riya"
4. How do you read input from the user?
(a) input()
(b) read()
(c) readLine()
(d) scanner()
► (c) readLine()
5. Which data type represents decimal numbers?
(a) Int
(b) Double
(c) Boolean
(d) Char
► (b) Double
6. Which operator is used for equality check?
(a) =
(b) ==
(c) ===
(d) !=
► (b) ==
7. Which statement is used for multiple conditional checks in Kotlin?
(a) if
(b) when
(c) switch
(d) select
► (b) when
8. How do you define a class in Kotlin?
(a) object
(b) struct
(c) class
(d) type
► (c) class
9. Which symbol is used for string templates?
(a) $
(b) @
(c) #
(d) &
► (a) $
10. Which type is used for true/false values?
(a) Boolean
(b) Int
(c) String
(d) Char
► (a) Boolean
11. How do you create a loop that executes at least once?
(a) for
(b) while
(c) do-while
(d) loop
► (c) do-while
12. Which of the following is immutable?
(a) var
(b) val
(c) varlate
(d) lateinit
► (b) val
13. What is the default return type of a function that does not return anything?
(a) Int
(b) Unit
(c) Void
(d) None
► (b) Unit
14. How do you convert a string to an integer?
(a) str.toInt()
(b) str.parseInt()
(c) int(str)
(d) str.int()
► (a) str.toInt()
15. Which keyword allows creating a singleton object?
(a) class
(b) object
(c) singleton
(d) instance
► (b) object
16. Which loop is best for iterating over a range?
(a) while
(b) do-while
(c) for
(d) loop
► (c) for
17. What does `!!` do in Kotlin?
(a) Converts to nullable
(b) Throws an exception if null
(c) Declares a variable
(d) Compares equality
► (b) Throws an exception if null
18. Which file extension is used for Kotlin files?
(a) .java
(b) .kt
(c) .kotlin
(d) .k
► (b) .kt