The slides for my talk at Devoxx BE 2018. Contents: Optional, method references over heavy lambdas, Passing-a-Block, Loan Pattern, Execute Around, Hiding Checked Exceptions, Method References on Enums. This talk was rated #1 talk of the whole conference.

1. VictorRentea.ro1
Functional Programming
Patterns With Java 8
- a live coding marathon -
@VictorRentea
www.VictorRentea.ro
Victor Rentea
Independent Trainer,
Lead Architect at IBM

2. Victor Rentea
14 years of Java
Clean Code Evangelist
VictorRentea.ro
Moscow Paris London Krakow Vienna Sofia Casablanca Belgrade Kiew Barcelona
.NET
+ more
Lead Architect
Tech Team Lead and Consultant
Software Craftsman
XP: Pair Programming, Refactoring, TDD
Bucharest
Software
Craftsmanship
Community
founder of

3. VictorRentea.ro @victorrentea victor.rentea@gmail.com
Independent
Technical Trainer & Coach
HibernateSpring Java 8
Architecture, DDDDesign Patterns
Clean Code Unit Testing, TDD
Java Performance and more…Scala
15 more…
100+ days1000 devs5 years
VictorRentea.rovictor.rentea@gmail.com
at:
follow me

4. VictorRentea.ro4
HARD-CORE SWITCH

5. VictorRentea.ro5
HARD-CORE SWITCH

6. VictorRentea.ro6
lower play rate
in YouTube

7. VictorRentea.ro7
Clean Code
Java 8
+

8. VictorRentea.ro8
Expressive Names
-> {
Lambdas should be one liners
Extract heavy lambdas into named ::methods
in the same class
in the item class
as static methods

9. VictorRentea.ro9
No Nullable Parameters
Avoid Returning Null, Throw Ex
Optional
Instead: thatOpt.map(doStuffWithIt)
…, or return an Optional
Even from Entity gettersMonad

10. VictorRentea.ro10
Execute arbitrary logic within a function
CPP
+1 boolean param
Extract & @Override
Template Method®
Passing-a-Block
exporter.exportFile("orders.csv", orderWriter::writeContent);

11. VictorRentea.ro11
The Loan Pattern
Passing-a-Block
try (Writer writer = new FileWriter(file)) {
contentWriter.accept(writer);
return file;
} catch (...) {
...
}
exporter.exportFile("orders.csv", orderWriter::writeContent);
contentWriter is "loaned"
a Writer managed here
similarly:
Testable
Infrastructure decoupled from export format
test with a dummy format test with a StringWriter

12. VictorRentea.ro12
Execute Around Pattern
Passing-a-Block
Ad-hoc Proxy® or Decorator®

13. VictorRentea.ro13
Rethrow Checked as Runtime
Prefer
Runtime Exceptions
Java8 functional interfaces don't throw anything
libs: jool, vavr, lombok

14. VictorRentea.ro14
switch
Switch Hunt Day
Hope to find them all: JDD
Simplest
1 switch = 1 method
case XX: return …
OOP
Extends is BAD
Combinatorial
Children90Movie
enum
Logic Bits
In enum methods
Logic with Dependencies
Function references on enums
Type-specific Logic

15. VictorRentea.ro15

16. VictorRentea.ro16

17. 17
Too
Disclaimer: The use of ® or ™ is the slides is only anecdotic. VictorRentea.ro
Thank You!
Let's chat!
Read it all in my dzone article
dzone.com/articles/functional-programming-patterns-with-java-8

18. 18
Too
VictorRentea.ro
I'm available
a statement of seniority
I use both hemispheres
Tough meetings?
Abused estimates?
Purpose of code:--Uncle Bob
1. Maintainable
2. Does its job!
Functional Party
Activist
Stay into
The Light
Trainings, talks, goodies
@VictorRentea
Quality posts daily on
Clean Code
needs strength
and determination
Thank You!
come take 1 sticker
Let's chat!
or a poster
Read it all in my dzone article
dzone.com/articles/functional-programming-patterns-with-java-8
(for tech leads)