30+ Android & Kotlin Interview Questions That Actually Confuse People

A single, tight reference covering the Kotlin and Android concepts most people get wrong — not because they’re obscure, but because they look simple and aren’t. Includes real “what does this print / what actually happens” traps and bugs pulled from real working code, not quiz snippets.

Table of Contents

1. Kotlin Fundamentals — Most Confused
2. OOP & Class Types
3. Coroutines & Flow — Where Most Confusion Lives
4. Jetpack Compose — Most Misunderstood
5. Architecture — MVVM vs Clean, For Real
6. Dependency Injection
7. Lifecycle & Memory
8. Testing
9. Scenario
10. Kotlin Language Traps (“What Does This Print?”)
11. Android Framework Traps (“What Actually Happens?”)
12. Bugs Hiding in Real Working Code

Kotlin Fundamentals — Most Confused

Q1. What is null safety in Kotlin? How does ?, !!, and ?: differ?

var name: String? = null

println(name?.length)        // null, no crash
println(name!!.length)       // 💥 NPE
println(name?.length ?: 0)   // 0