Kotlin Brain Teasers

Exercise Your Mind

by Sam Cooper

Can you outsmart the Kotlin compiler? Detect, deduce, and diagnose your way to clearer code and expert insights. Escape type-system traps and navigate logic labyrinths. Challenge your skills and quiz your friends with fun Kotlin facts, and power up your code with nuanced mastery of data types, functions, and programming techniques. Stay sharp, know your threats, and reason critically to fix bugs before they happen. Laugh at unexpected outcomes and puzzle over awkward edge cases, then ace your next interview with memorable payoffs that simplify key concepts in Kotlin and computer science.

Put the fun in functions and laugh while you learn with programming puzzles that challenge your intuition and sharpen your skills. Guess each simple program’s output—if you can—then run the code or turn the page to find out what’s not as it seems. Deepen your understanding of key data types and put computer science in context as you make deductions and discoveries that will upgrade your apps. Play around and break things to uncover the deliberate design decisions behind Kotlin’s unexpected quirks and reveal the why, not just the what.

Take on the type system and smuggle null values past the compiler’s defenses. Overload operators and turn math on its head as you crack floating-point conundrums. Think like a computer and predict your program’s path when you test the limits of control-flow keywords. Harness the power of iteration and immutability to tame devious data and curate collections with confidence. Unravel ambiguous lambda functions and streamline inscrutable syntax. Dodge destructuring dilemmas, spot sneaky shadowing, and know the dynamic difference between members and extensions.

Prepare for interviews, tests, competitions, real-world projects, and more with powered-up problem-solving proficiency, improved coding confidence, and lasting Kotlin lessons. Most of all, have fun!

• Errata, typos, suggestions

• Source Code (zip file)

Releases:

• P1.0 2025/09/14
• B5.0 2025/08/20
• B4.0 2025/07/14
• B3.0 2025/06/30

• Introduction
• Something From Nothing?
• Elvis In The Building
• As Close As It Gets
• Upside-Down Math
• Is It A Number Or Not?
• Which Came First?
• Anything You Want Me To Be
• What’s In The Box?
• That’s Not What I Ordered
• How Deep Is Your Copy?
• This Much Is True
• It’s Over Nine Thousand!
• Who You Gonna Call?
• Just One More Thing
• End Of The Line
• The Vacuous Boomerang
• Don’t Bet On It
• A Class With No Name?
• It’s Just An Expression
• Never The Same
• Serial Spending Problem
• Inside, Outside
• Bringing Up The Rear