Kotlin Certification

Kotlin certification syllabus & coverage

This certification tests genuine comprehension of Kotlin language fundamentals, idiomatic patterns, data structures, and production practices. Questions are sampled across all course modules:

• Getting Started: Why Kotlin runs Android and modern JVM backends, how to install it on any OS, and your first Kotlin program compiled, run and explained.
• Fundamentals: val versus var, type inference, the basic types, strings and templates, operators, reading input with readln(), converting types safely, and ranges.
• Flow Control: if and when as expressions, for loops over ranges with until, downTo and step, while and do-while, labeled break and continue, and repeat.
• Functions & Lambdas: Declare functions with default, named and vararg parameters, then treat functions as values: lambdas, function types, trailing lambdas, higher-order functions and tailrec.
• Null Safety: Nullable types, ?., ?:, !!, smart casts, as?, let, lateinit and lazy, Java platform types, and the NullPointerExceptions Kotlin still lets through.
• Collections: Kotlin lists, sets and maps: read-only vs mutable, arrays vs lists, the transformation functions you use daily, and lazy sequences.
• Classes & Objects: Kotlin classes from the ground up: constructors, init blocks, properties with custom getters and setters, visibility, companions and inner classes.
• Inheritance & Interfaces: Kotlin inheritance done right: open and override, abstract classes, interfaces with default methods, polymorphism, delegation with by, and type checks.
• Data, Sealed & Enum Classes: Data classes, copy and destructuring, enum classes with behaviour, sealed hierarchies with exhaustive when, value classes and objects for modeling state.
• Generics & Extensions: Generic classes and functions, in/out variance, reified types, extension functions, scope functions, operators and delegation with by, lazy and observable.
• Coroutines: Suspend functions, launch and async, structured concurrency, dispatchers, cancellation, exceptions, Flow and Channels, and viewModelScope on Android.
• Errors & Debugging: The 15 Kotlin errors beginners hit most, with the real compiler and JVM messages, how to read a stack trace, and how to debug and log.
• Kotlin + Tools: Nine mini-labs on Kotlin as it is used at work: Gradle, JUnit 5, Ktor, Spring Boot, PostgreSQL, Android, Jetpack Compose, Docker and Git.
• Data Structures & Algorithms: Stacks, queues, linked lists, trees, heaps and graphs in Kotlin — built by hand, then with the stdlib — plus binary search, sorting and DP.
• Problem Solving: A repeatable method for coding problems and the eight patterns behind most of them, each worked end to end in idiomatic Kotlin.
• Interview Questions: Sixty Kotlin interview questions — 25 junior, 25 mid-level, 10 senior — with model answers, what each tests, a coding round and a take-home checklist.
• Job Ready: What a Kotlin resume must show for Android and backend roles, three portfolio projects that get callbacks, where Kotlin jobs are, and the exam.

Exam rules & grading

The exam features 25 multiple-choice questions with a time limit of 35 minutes. A passing score of 70% or higher issues a permanent certificate with a verifiable credential ID that can be attached directly to your resume and LinkedIn Profile.

Frequently asked questions