Kotlin · CodeWiki

All beginner intermediate advanced

show All Unread Read

01 · Basics

3 topics

Collections Kotlin's core collection types, mutation boundaries, operation pipelines, and lazy sequences, including aliasing and key-collision traps. intermediate 18 min Kotlin fundamentals Learn Kotlin's read-only references, static types, null safety, expressions, control flow, and function-call boundaries. beginner 17 min Null safety Model missing values with nullable types, smart casts, safe calls, and Elvis, then keep NPEs out of Java and generated-code boundaries. beginner 17 min

02 · Functions and classes

9 topics

Data classes Define data-class value semantics, understand generated equality, destructuring, and shallow copies, and avoid mutable-key, array, and secret-field traps. intermediate 17 min Delegated properties Move Kotlin getter and setter logic into reusable delegates, with precise guidance for lazy, observable, custom delegates, shared state, and thread safety. intermediate 15 min DSLs Design Kotlin internal DSLs with lambdas with receivers, type-safe builders, explicit scope control, and verifiable result boundaries. advanced 13 min Extensions Add functions and computed properties to existing types with receiver syntax, then reason about static resolution, member precedence, nullability, and scope. intermediate 13 min Inline value classes Model single-value domain types with `@JvmInline value class`, including JVM representation, boxing boundaries, validation, and Java interop. intermediate 14 min Lambda expressions Lambda expressions turn behavior into statically typed values; learn function types, capture, receivers, return control, and JVM boundaries. intermediate 19 min Object-oriented programming Build clear object boundaries with classes, interfaces, inheritance, and composition; understand Kotlin's final defaults, dispatch, and construction order. intermediate 15 min Scope functions Choose among Kotlin's let, run, with, apply, and also by receiver and return value, without nullable, nested-receiver, or chain-type mistakes. intermediate 14 min Sealed classes and interfaces Model finite states with restricted hierarchies, use exhaustive when to catch new cases, and choose correctly among sealed classes, interfaces, and enums. intermediate 16 min