Working with Java & Kotlin

The presentation shows how Kotlin fits in the Java Ecosystem while demonstrating some basic language features using sample code: console, spring boot and android app

Transcript

1. @charlesmuchene Working with Java & Kotlin
2. Agenda • What is Kotlin? • Kotlin - Java interoperability • Kotlin on Spring • Kotlin on Android
3. Compilation Java Source Java Compiler Java Bytecode Student.java Student.class
4. Compilation + Execution Sources Bytecode JVM Application
5. Execution Bytecode JVM Application
6. JVM Kotlin Java
7. Why Kotlin? Concise Safe Interoperable Tooling
8. Kotlin Android JVM Web Native
9. Kotlin Android JVM Web Native
10. Code demo
11. Kotlin + Spring
12. Person RESTful API
13. Application File @SpringBootApplication class Application fun main(args: Array<String>) { runApplication<Application>(*args) }
14. Person Controller @RestController class PersonController(private val personRepository: PersonRepository) { @GetMapping("/person") fun readAll() = personRepository.findAll() @GetMapping("/person/{id}") fun readOne(@PathVariable id: Long) = personRepository.findById(id) }
15. Person Class @Entity data class Person(@Id val id: Long, val firstName: String, ...
16. Running Spring Boot App
17. App demo
18. Kotlin + Android
19. Countries App
20. Countries App Flow Launch Fetch online Display
22. Main Activity class MainActivity : AppCompatActivity() { private lateinit var viewModel: CountryViewModel private var countryAdapter = CountryAdapter() override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) ... } ...
23. Country Details ViewModel class CountryDetailsViewModel : ViewModel() { fun getDetails(country: Country): String = with(country) { """ Native Name: $nativeName Demonym: ${demonym.orDash} Population: ${String.format("%,d", population)} Language(s): ${languages.joinToString(transform = Language::toString)} Currency: ${currencies.joinToString(transform = Currency::toString)} Timezone(s): ${timezones.joinToString()} """.trimIndent() } }
24. Country Class @Parcelize data class Country(val name: String, val capital: String, ...
25. App demo
26. Kotlin Love - StackOverflow https://insights.stackoverflow.com/survey/2018/#technology
27. Kotlin Interest - StackOverflow https://insights.stackoverflow.com/survey/2018/#technology
28. Kotlin Interest - Hackerrank https://research.hackerrank.com/developer-skills/2019
29. Resources • https://kotlinlang.org/ • https://insights.stackoverflow.com/survey/2018 • https://research.hackerrank.com/developer-skills/2019 • https://github.com/charlesmuchene/learn-kotlin-app • https://github.com/charlesmuchene/learn-kotlin-jvm • https://github.com/charlesmuchene/learn-kotlin-spring-boot
30. charlesmuchene