Kotlin from-scratch
0 likes206 views
The document provides an overview of the Kotlin programming language, including what it is, who created it, when it was created, where it can be used, and why it is useful. Specifically: - Kotlin is a programming language created by JetBrains as an alternative to Java that compiles to JVM bytecode. - It was created in 2010 and became open source in 2012, with stable releases beginning in 2016 and support on Android announced by Google in 2017. - Kotlin can run on the JVM for Android and server-side applications as well as JavaScript and native platforms, though cross-platform code cannot use Java libraries. - Advantages include being modern, concise,
Kotlin from-scratch
- 1. Kotlin from scratch [email protected] - https://www.linkedin.com/in/francolombardo/
- 2. Kotlin The five Wh questions • What? • Who? • When? • Where? • Why?
- 3. What is Kotlin? Kotlin is a programming language with a syntax similar to C / Java / JavaScript / C# • Strong typing (a number is not a string) • Static typing (types of variables are checked at compile time) • Type inference (type declaration can often be omitted) • Object Oriented Programming (classes, objects, methods, inheritance, polymorphic calls) • Functional Programming Paradigm (functions are types, so we can pass them around)
- 4. Who created Kotlin? • Kotlin was created by JetBrains, a company that builds programming languages IDEs and tools such as IntelliJ IDEA • There is a Kotlin Foundation created with Google to protect the trademarks and to design the development path • Open source licensed under Apache 2 • Kotlin is the name of an island near St. Petersburg (Java is the name of an island, too)
- 5. When was Kotlin created? • 2010: Start of the Kotlin project • 2012: The project becomes Open Source • 2016: First stable release • 2017: Google announces support on Android • 2019: It becomes the preferred language for Android
- 6. Where does Kotlin run? • JVM: primary target, the only one that is battle-proven • JS: browser and server (NodeJS) (early stage) • Native: iOS and more (early stage) Be careful: cross platform code cannot use Java libraries!
- 7. Why Kotlin? • It’s modern (OOP + functional + coroutines +…) • It’s concise • It’s interoperable • it can reuse Java libraries ecosystem • it can be used by Java projects • It’s multiplatform (maybe?) • It handles null values in a safer way • Decoupling the evolution of the language from the evolution of the JVM (e.g. phones, AS400, mission critical production servers)
- 8. Why Kotlin? Working in Kotlin is a lot of fun! J
- 9. The very recommended IDE for Kotlin
- 10. The very recommended IDE for Kotlin
- 11. The very recommended IDE for Kotlin
- 12. The very recommended building system for Kotlin Sample project: https://github.com/f-lombardo/kotlin-from-scratch
- 13. Strong static typing with inference fun main() { val authorOfNabucco: String = "Giuseppe Verdi" val authorOfTurandot = "Giacomo Puccini" println("Italian composers: $authorOfNabucco and $authorOfTurandot") }
- 14. Strong static typing with inference fun main() { val authorOfNabucco: String = "Giuseppe Verdi" val authorOfTurandot = "Giacomo Puccini" println("Italian composers: $authorOfNabucco and $authorOfTurandot") } Explicit type declaration Type inference String interpolation Immutable variables are preferred
- 15. Multiline strings: Kotlin is concise Test blocks of RPG CODE easily
- 16. Kotlin is concise: why is it important? Concise ↓ Less boilerplate code ↓ Easier to understand (less cognitive overload) ↓ Fewer bugs
- 17. How much is Kotlin concise? Data class: Java Bean with hashCode, toString, equals and much more
- 18. How much is Kotlin concise? Decompiled Java version of the previous data class (just a part of it)
- 19. Default arguments Default arguments = less overloading!!!
- 20. Kotlin is safer Can be null Cannot be null val italianComposer: String = "Giuseppe Verdi" val dutchComposer: String? = null
- 21. val result = openDatabase("franco", "secret") ?.findFirstComposerByNation("Italy") ?.findOperaByYear(1871) ?: "No results" Kotlin is safer Composing nullable values/functions in a safe way Possibly null Not null
- 22. val result = openDatabase("franco", "secret") ?.findFirstComposerByNation("Italy") ?.findOperaByYear(1871) ?: "No results" Kotlin is safer Composing nullable values/functions in an expressive way “or else”“and then”
- 23. Extension functions data class Database(val composers: List<Composer>) data class Composer(val name: String, val nation: String, val operas: List<Opera>) data class Opera(val name: String, val yearOfComposition: Int) fun Database.findFirstComposerByNation(nation: String): Composer? = this.composers.firstOrNull { it.nation == nation } fun Composer.findOperaByYear(year: Int): Opera? = this.operas.firstOrNull { it.yearOfComposition == year } Extending classes from outside
- 24. Extension functions Code organization based on domain aspects Extension methods for domain objects regarding the “SQL aspect”
- 25. The power of lambdas val elapsedTime = measureTimeMillis { execute(compilationUnit.main.stmts) } public fun measureTimeMillis(block: () -> Unit): Long { val start = System.currentTimeMillis() block() return System.currentTimeMillis() - start }
- 26. References Kotlin in action Dmitry Jemerov, Svetlana Isakova Kotlin for Java Developers https://www.coursera.org/learn/kotlin-for-java-developers JetBrains Kotlin Academy https://hyperskill.org/onboarding/?track=kotlin JetBrains Kotlin playlist on YouTube https://bit.ly/kotlinTube Kotlin hands-on labs (Coroutines, JS, Native) https://play.kotlinlang.org/hands-on/overview