Practical Functional Java

Workshop Overview

Jeff Butler

https://github.com/jeffgbutler/practical-functional-java

https://jeffgbutler.github.io/practical-functional-java/

About Me

• Enterprise Architect for DMI in Indianapolis
• Committer to Apache iBatis/MyBatis since 2005
• Creator of MyBatis Generator and MyBatis Dynamic SQL
• Voracious reader, adventurous eater, lawn care enthusiast
• Desert Island disks include White Stripes, Beck, Nirvana, Jimmie Dale Gilmore, Marty Stuart

How this Workshop Came to Be

• I finally learned JavaScript
• Java 8 Study Group
• "Clean Code" Book Clubs at DMI and our clients
• MyBatis Dynamic SQL
• These experiences have changed the way I think about coding.

Plan for the Workshop

• Some thoughts about Functional Programming
• Immutability Review and Exercises
• Lambda Review
• Streams Review and Exercises
• Optionals Review
• Multi-step guided exercise - Green Field
• Function Composition Review
• Multi-step guided exercise - Refactoring
• Coda: Advanced Immutability

Focus on Practical - Very Few $10 Vocabulary Words!

Functional Programming Hype

• Solves all your concurrency problems!
• The solution to Moore's Law slowing down!
• Super Trendy! Big Money!
• Retro/Vintage/Hipster Programming - Lisp is Cool Again!

But seriously, how many people in this room...

• have major concurrency problems?
• have a Moore's Law problem?

Why Are We Here?

I want to be a functional programmer!

Wrong answer

I want to be a better programmer!

This is why we're here...

What is clean code?

• Meaningful Names
• Small Methods
• Small Classes
• TDD
• SOLID Principles

Functional practices urge us towards clean code

What is Functional Programming?

• Functions as first class citizens?
• Pure functions?
• Lambdas?
• Closures?
• Recursion with Tail Call Optimization?
• Lazy streams?
• Immutability?
• Declarative vs. Imperative?
• Monads (Haskell)?
• Code as Data (Lisp)?

Argh!

No one can define it!

Except maybe Uncle Bob...

Spoiler alert...Immutability is the Key!

Next Steps

• Demo and overview of the source repo
• Setup Exercise: Make sure you can run the tests in whatever IDE you choose