Kotlin Syntax

 Kotlin Syntax – Complete Beginner Guide

Kotlin is a modern, concise, and safe programming language mainly used for Android development, but also for backend, web, and desktop apps.

 1. Hello World Program

• fun → function keyword
• main() → entry point
• println() → prints output

2. Variables in Kotlin

val (Immutable – cannot change)

var (Mutable – can change)

•  Kotlin encourages val over var

3. Data Types

Kotlin is statically typed, but supports type inference.

Common Types

• Int

• Long

• Float

• Double

• Boolean

• String

• Char

 4. Type Inference

Compiler automatically detects type:

•  Cleaner syntax
•  Less boilerplate

 5. Comments

Single-line

Multi-line

 6. String Templates (Very Important)

•  No need for + concatenation

 7. Conditional Statements

 if – else

 if as Expression

•  Kotlin treats if as an expression

 8. When Statement (switch replacement)

•  More powerful than switch

 9. Loops

 for loop

 while loop

 do-while loop

10. Functions

Short Function (Single Expression)

•  Clean and concise

11. Null Safety (Kotlin’s Superpower)

Nullable Variable

Safe Call

Elvis Operator

 NullPointerException avoided!

12. Arrays & Collections

Array

List

Map

 13. Class & Object

•  Constructor built-in
•  Less boilerplate than Java

14. Data Class

 Auto generates:

• toString()

• equals()

• hashCode()

• copy()

15. Companion Object (Static Alternative)

Call:

 Common Kotlin Syntax Mistakes

• Using var everywhere

• Ignoring null safety

• Forgetting else in when

• Using Java-style code

 Best Practices

•  Prefer val
•  Use expression syntax
•  Handle nulls properly
•  Keep functions small
•  Write idiomatic Kotlin

 Interview Quick Questions

Q1. Is Kotlin statically typed?
Yes.

Q2. Difference between val and var?
val = read-only, var = mutable

Q3. Kotlin alternative to switch?
when

Q4. Can Kotlin run on JVM?
Yes.

 Summary

•  Simple & expressive syntax
•  Less boilerplate than Java
•  Built-in null safety
•  Perfect for Android & backend