Slides from my presentation at WeAreDevelopers 2023 in Berlin

1. Modern Java
Ron Veen
WeAreDevelopers - Berlin - 2023

2. Who is Ron Veen
@ronveen
ronveen
@ronveen@foojay.social
● Java developer for 20+ years
● Special Agent @ Team Rockstars IT
● Writing a book about Migrating to cloud-native Jakarta EE

3. Agenda
1. Records, sealed classes and pattern matching
2. Virtual threads, structured concurrency, scoped values
3. What else is in Java 21
4. Examples of modern Java

4. Part 1 - Records, sealed classes and pattern matching

5. Records

6. Sealed classes

7. Pattern Matching
● Predicate
● Object to test against
● Pattern variables
● Flow scope

8. Pattern Matching: Instanceof
● Predicate ==> instanceof Approver
● Object to test against ==> user
● Pattern variables ==> a
● Flow scope ==> between { }

9. Pattern Matching: switch

10. Pattern Matching: record

11. Part 2 - Virtual Threads, Structured Concurreny, Scoped Values

12. Java Threads

13. Virtual Threads

14. Factory methods

15. Virtual Thread Per Task Executor

16. Structured Concurrency

17. Invoke All pattern

18. Invoke Any pattern

19. Thread Locals
1. Share information between different components of your application
2. Create a ThreadLocal instance that is reachable from anywhere
3. You can provide an initial value on creation
4. Or set a value using set (T value)
5. Retrieve the value anywhere via get( )

20. The problem with Thread Locals
1. Mutable
2. Resource intensive
3. Leaking

21. Enter Scoped Values
1. Exist for a limited time (lifetime of the Runnable)
2. Only the thread that wrote the value can read it
3. Immutable
4. Passed by reference

22. Scoped Values

23. Part 3 - What else is new in Java 21

24. Agenda
1. Simpler main methods
2. Unnamed classes
3. Unnamed variables
4. Sequenced Collections
5. String Templates

25. Simpler main methods

26. Unnamed classes

27. Unnamed variables

28. Unnamed variables

29. Unnamed variables

30. Sequenced Collections

31. Sequenced Collections

32. String templates

33. String templates

34. String templates

35. Part 4 - Combining Java and data-oriented programming

36. Data-oriented programming

37. Principles of data-oriented programming
● Separate data from logic
● Data is stored in generic data structures
● Data is immutable

38. Alternative optional

39. Usage of data-oriented programming

40. Summary
● Data-oriented programming treats data as first-class citizens
● Data drives your application
● Java supports data-oriented programming via records, sealed classes and pattern matching

41. Questions