This document summarizes a presentation about choosing between Java 11 and Kotlin for upgrading code. It highlights new features in Java 11 like switch statements and collection convenience methods. It also discusses the presenter's experience migrating code from Java to Kotlin by making stream operations and repository calls more readable. Reasons given to switch to Kotlin include regular updates, interoperability, less boilerplate, and safe programming. The document ends by outlining a migration plan and encouraging trying Kotlin in proof of concepts first.

1. Upgrade Time! Choose Java 11
or the other one… Kotlin!
Paulien van Alst
Amsterdam | April 2-3, 2019

2. Who am I?
@PaulienVanAlst

3. Highlights Java 9/10/11
switch statements
var something = “Something”
JShell
Convenience methods for collections
Release cadence

4. My story with Kotlin
boardGameRepository.findAllByCategory(ADVENTURE).stream()
.filter(game -> game.getMinimalNumberOfPlayers() > 2)
.filter(game -> game.getMinimalAge() > 10)
.map(BoardGameEntity::getPrice)
.reduce(BigDecimal.ZERO, BigDecimal::add);

5. My story with Kotlin
boardGameRepository.findAllByCategory(ADVENTURE).stream()
.filter(game -> game.getMinimalNumberOfPlayers() > 2)
.filter(game -> game.getMinimalAge() > 10)
.map(BoardGameEntity::getPrice)
.reduce(BigDecimal.ZERO, BigDecimal::add);
boardGameRepository.findAllByCategory(ADVENTURE)
.moreThanTwoPlayers()
.olderThanTenToPlay()
.meanPrice()

6. My story with Kotlin
boardGameRepository.findAllByCategory(ADVENTURE).stream()
.filter(game -> game.getMinimalNumberOfPlayers() > 2)
.filter(game -> game.getMinimalAge() > 10)
.map(BoardGameEntity::getPrice)
.reduce(BigDecimal.ZERO, BigDecimal::add);
boardGameRepository.findAllByCategory(ADVENTURE)
.moreThanTwoPlayers()
.olderThanTenToPlay()
.meanPrice()

7. My story with Kotlin
boardGameRepository.findAllByCategory(ADVENTURE).stream()
.filter(game -> game.getMinimalNumberOfPlayers() > 2)
.filter(game -> game.getMinimalAge() > 10)
.map(BoardGameEntity::getPrice)
.reduce(BigDecimal.ZERO, BigDecimal::add);
boardGameRepository.findAllByCategory(ADVENTURE)
.moreThanTwoPlayers()
.olderThanTenToPlay()
.meanPrice()

8. My story with Kotlin
boardGameRepository.findAllByCategory(ADVENTURE).stream()
.filter(game -> game.getMinimalNumberOfPlayers() > 2)
.filter(game -> game.getMinimalAge() > 10)
.map(BoardGameEntity::getPrice)
.reduce(BigDecimal.ZERO, BigDecimal::add);
boardGameRepository.findAllByCategory(ADVENTURE)
.moreThanTwoPlayers()
.olderThanTenToPlay()
.meanPrice()

9. My story with Kotlin
boardGameRepository.findAllByCategory(ADVENTURE).stream()
.filter(game -> game.getMinimalNumberOfPlayers() > 2)
.filter(game -> game.getMinimalAge() > 10)
.map(BoardGameEntity::getPrice)
.reduce(BigDecimal.ZERO, BigDecimal::add);
boardGameRepository.findAllByCategory(ADVENTURE)
.moreThanTwoPlayers()
.olderThanTenToPlay()
.meanPrice()

10. Reasons to switch to Kotlin
Regular updates
Interoperability
Multiplatform
Readability
Less boilerplate
Safe programming

11. What to keep in mind
Interoperability
Idioms
Magic problem solver

12. Warning!
DO this at home
or
In a POC

13. Let’s start!
Rates 6 8
Games above … 8 9 9,5

14. Let’s start!
Spring boot 2
In memory database
UT’s and IT’s

15. Migration Plan
1. Set-up dependencies
2. Migrate PoJo’s
3. Rewrite unit tests
4. Core logic
5. Configuration
6. Test DSL

16. Let’s start
Code!

17. Migration Plan
1. Set-up dependencies
2. Migrate PoJo’s
3. Rewrite unit tests
4. Core logic
5. Configuration
6. Test DSL

19. Thank you!
Rate this talk!