Kotlin is a cross-platform, statically typed, general-purpose programming language with type inference. Kotlin is a more modern version of Java. It adopts functional ideas such as immutability and first-class functions, out of the box, and it is also object oriented.
Kotlin is designed to interoperate fully with Java, and the JVM version of its standard library depends on the Java Class Library, but type inference allows its syntax to be more concise. Kotlin mainly targets the JVM, but also compiles to JavaScript or native code (via LLVM).
Kotlin has been making waves since it was open sourced by JetBrains in 2011; it has been praised by developers across the world and is being adopted by companies.
Kotlin is published under the Apache License 2.0.
There are very few free books available for Kotlin. For more Kotlin-released resources, read our recommended free Kotlin tutorials.
1. Essential Kotlin maintained by Krzysztof Kowalczyk
Essential Kotlin is a free book about the Kotlin programming language.
It’s written to provide clear and concise explanation of topics for both beginner and advanced programmers.
Most examples are linked to online playground that allows you to change the code and re-run it.
The content is based on now abandoned StackOverflow Documentation project.
2. Kotlin Quick Reference by Alvin Alexander
Kotlin Quick Reference is intended to provide a quick reference to the Kotlin programming language. The idea is to show Kotlin syntax and examples with as few words as possible so that experienced developers who are new to Kotlin can find what they need quickly.
The target audience for this book is someone who already knows languages like Java and Scala and just needs a very quick reference to Kotlin’s syntax and some corresponding examples so they can be productive.
Each chapter in the book demonstrates Kotlin syntax and provides examples to explain the chapter’s topic. This is done in a brisk manner, with as few words as necessary.
All books in this series:
| Free Programming Books | |
|---|---|
| Ada | ALGOL-like programming language, extended from Pascal and other languages |
| Agda | Dependently typed functional language based on intuitionistic Type Theory |
| Arduino | Inexpensive, flexible, open source microcontroller platform |
| Assembly | As close to writing machine code without writing in pure hexadecimal |
| Awk | Versatile language designed for pattern scanning and processing language |
| Bash | Shell and command language; popular both as a shell and a scripting language |
| BASIC | Beginner’s All-purpose Symbolic Instruction Code |
| C | General-purpose, procedural, portable, high-level language |
| C++ | General-purpose, portable, free-form, multi-paradigm language |
| C# | Combines the power and flexibility of C++ with the simplicity of Visual Basic |
| Clojure | Dialect of the Lisp programming language |
| ClojureScript | Compiler for Clojure that targets JavaScript |
| COBOL | Common Business-Oriented Language |
| CoffeeScript | Transcompiles into JavaScript inspired by Ruby, Python and Haskell |
| Coq | Dependently typed language similar to Agda, Idris, F* and others |
| Crystal | General-purpose, concurrent, multi-paradigm, object-oriented language |
| CSS | CSS (Cascading Style Sheets) specifies a web page’s appearance |
| D | General-purpose systems programming language with a C-like syntax |
| Dart | Client-optimized language for fast apps on multiple platforms |
| Dylan | Multi-paradigm language supporting functional and object-oriented coding |
| ECMAScript | Best known as the language embedded in web browsers |
| Eiffel | Object-oriented language designed by Bertrand Meyer |
| Elixir | Relatively new functional language running on the Erlang virtual machine |
| Erlang | General-purpose, concurrent, declarative, functional language |
| F# | Uses functional, imperative, and object-oriented programming methods |
| Factor | Dynamic stack-based programming language |
| Forth | Imperative stack-based programming language |
| Fortran | The first high-level language, using the first compiler |
| Go | Compiled, statically typed programming language |
| Groovy | Powerful, optionally typed and dynamic language |
| Haskell | Standardized, general-purpose, polymorphically, statically typed language |
| HTML | HyperText Markup Language |
| Icon | Wide variety of features for processing and presenting symbolic data |
| J | Array programming language based primarily on APL |
| Java | General-purpose, concurrent, class-based, object-oriented, high-level language |
| JavaScript | Interpreted, prototype-based, scripting language |
| Julia | High-level, high-performance language for technical computing |
| Kotlin | More modern version of Java |
| LabVIEW | Designed to enable domain experts to build power systems quickly |
| LaTeX | Professional document preparation system and document markup language |
| Lisp | Unique features - excellent to study programming constructs |
| Logo | Dialect of Lisp that features interactivity, modularity, extensibility |
| Lua | Designed as an embeddable scripting language |
| Markdown | Plain text formatting syntax designed to be easy-to-read and easy-to-write |
| Objective-C | Object-oriented language that adds Smalltalk-style messaging to C |
| OCaml | The main implementation of the Caml language |
| Pascal | Imperative and procedural language designed in the late 1960s |
| Perl | High-level, general-purpose, interpreted, scripting, dynamic language |
| PHP | PHP has been at the helm of the web for many years |
| PostScript | Interpreted, stack-based and Turing complete language |
| Prolog | A general purpose, declarative, logic programming language |
| PureScript | Small strongly, statically typed language compiling to JavaScript |
| Python | General-purpose, structured, powerful language |
| QML | Hierarchical declarative language for user interface layout - JSON-like syntax |
| R | De facto standard among statisticians and data analysts |
| Racket | General-purpose, object-oriented, multi-paradigm, functional language |
| Raku | Member of the Perl family of programming languages |
| Ruby | General purpose, scripting, structured, flexible, fully object-oriented language |
| Rust | Ideal for systems, embedded, and other performance critical code |
| Scala | Modern, object-functional, multi-paradigm, Java-based language |
| Scheme | A general-purpose, functional language descended from Lisp and Algol |
| Scratch | Visual programming language designed for 8-16 year-old children |
| SQL | Access and manipulate data held in a relational database management system |
| Standard ML | General-purpose functional language characterized as "Lisp with types" |
| Swift | Powerful and intuitive general-purpose programming language |
| Tcl | Dynamic language based on concepts of Lisp, C, and Unix shells |
| TeX | Markup and programming language - create professional quality typeset text |
| TypeScript | Strict syntactical superset of JavaScript adding optional static typing |
| Vala | Object-oriented language, syntactically similar to C# |
| VHDL | Hardware description language used in electronic design automation |
| VimL | Powerful scripting language of the Vim editor |
| XML | Rules for defining semantic tags describing structure ad meaning |