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
   

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2. Agenda
   • What is Kotlin?
   • Kotlin - Java interoperability
   • Kotlin on Spring
   • Kotlin on Android
   

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3. Compilation
   Java Source Java Compiler Java Bytecode
   Student.java Student.class
   

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4. Compilation + Execution
   Sources
   Bytecode
   JVM
   Application
   

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5. Execution
   Bytecode JVM Application
   

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6. JVM
   Kotlin
   Java
   

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7. Why Kotlin?
   Concise Safe Interoperable Tooling
   

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8. Kotlin
   Android
   JVM Web Native
   

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9. Kotlin
   Android
   JVM
   Web Native
   

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10. Code demo
    

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11. Kotlin + Spring
    

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12. Person RESTful API
    

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13. Application File
    @SpringBootApplication
    class Application
    fun main(args: Array) {
    runApplication(*args)
    }
    

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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)
    }
    

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15. Person Class
    @Entity
    data class Person(@Id val id: Long, val firstName: String, ...
    

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16. Running Spring Boot App
    

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17. App demo
    

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18. Kotlin + Android
    

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19. Countries App
    

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20. Countries App Flow
    Launch Fetch online Display
    

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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)
    ...
    }
    ...
    

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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()
    }
    }
    

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24. Country Class
    @Parcelize
    data class Country(val name: String, val capital: String, ...
    

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25. App demo
    

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26. Kotlin Love - StackOverflow
    https://insights.stackoverflow.com/survey/2018/#technology
    

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27. Kotlin Interest - StackOverflow
    https://insights.stackoverflow.com/survey/2018/#technology
    

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28. Kotlin Interest - Hackerrank
    https://research.hackerrank.com/developer-skills/2019
    

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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
    

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30. charlesmuchene
    

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