Achieving Functional Programming in Java

GOTO Chicago 2019

For years, the conventional wisdom around attempting pure functional programming in Java has been "don't", and for plenty of good reasons: lambdas weren't supported until the eighth major release of the language specification, creating value types is a verbose, ceremony-riddled exercise devoid of any first-class syntax, and neither are the majority of the data structures shipped in the JDK immutable, nor are interfaces a proper substitute in general for type classes.

Still, it's a shame for developers to have to seemingly choose between the myriad benefits of functional programming and the maturity of the java compiler, the investments made into the ecosystem by major organizations, and the ease of hireability especially when some of these short-comings can be addressed externally.

In this talk I'll present Lambda, a Java library that offers:

• A first-class model for functors, applicative functors, monads, coproducts, and more algebraic and category theoretic structures
• Lazy evaluation
• Profunctor optics
• Semigroups and Monoids
• Type-safe heterogeneous structures like HLists and HMaps
• and more...

The goal of this talk is to present this library as a viable option for experienced Java development teams that wish they could use some of the functional programming capabilities available in languages like Haskell?, and to show how the trading infrastructure teams of an algorithmic-trading firm in Chicago use Lambda to write correct-by-construction software and accelerate their development process.

Who should attend this talk: Experienced Java developers who want to program using algebraic data types, compositional patterns like functors and monads, lazy evaluation strategies, and a strong emphasis on type-level transformations, but are daunted by Java's current limitations in these areas

Academic level: Advanced to Expert

What is the take away in this talk: While Java has a long way to go, libraries like Lambda enable developers who want to push their Java programming much further towards functional idioms that previously seemed unachievable