Learn Kotlin

Kotlin Topics

Click on a topic to expand and learn in detail.

• 1. Introduction to Kotlin

fun main() {
    println("Hello, Kotlin!")
}
      

Kotlin is modern, concise, safe, and interoperable with Java, mainly for Android apps.

• 2. Variables & Constants

var age = 25      // mutable
val name = "Alice" // immutable
val pi: Double = 3.14
      

Use var for changeable values, val for constants.

• 3. Operators

// Arithmetic
val sum = 5 + 3

// Comparison
val isAdult = age >= 18

// Logical
val flag = isAdult && true
      

Operators perform arithmetic, comparison, and logical operations.

• 4. Conditions

if(age >= 18){
    println("Adult")
} else {
    println("Minor")
}

// When (like switch)
when(age){
    18 -> println("Exactly 18")
    else -> println("Other age")
}
      

Use if-else or when to control program flow.

• 5. Loops

// for loop
for(i in 0..4){
    println(i)
}

// while loop
var j = 0
while(j < 5){
    println(j)
    j++
}

// do-while
var k = 0
do {
    println(k)
    k++
} while(k < 5)
      

Loops repeat code multiple times.

• 6. Functions

fun add(a: Int, b: Int): Int {
    return a + b
}
println(add(5,3))
      

Functions are reusable code blocks that can return values.

• 7. Object-Oriented Programming

class Person(val name: String, var age: Int){
    fun greet(){
        println("Hello $name")
    }
}

val p = Person("Alice", 25)
p.greet()
      

Kotlin supports OOP concepts: Classes, Objects, Inheritance, and Polymorphism.

• 8. Advanced Kotlin
• Null Safety & Optionals
• Higher-Order Functions
• Lambda Expressions
• Generics & Collections
• Coroutines (Asynchronous Programming)

// Lambda
val square = { x: Int -> x * x }
println(square(5))

// Null Safety
var name: String? = null
println(name ?: "No Name")