Functional Java

ABSTRACT

Functional Java

This talk covers the main features of functional programming in Java. We’ll learn a bit about functional programming concept before diving into how Oracle implemented it in Java. We’ll then cover some new features like Streams and Optional that enable a functional programming style.
Functional Interfaces
To support a functional programming style, Oracle introduced a few features to the Java language, since version 1.8.

This part will cover the core feature of Java 8, that is the possibility to represent functions as objects. In order to achieve this, we’ll go through a few functional interfaces like Function, Predicate, Consumer and Supplier.

We’ll then have a word about lambda expressions and how they map to those objects (and others). With that seen, we’ll be able to learn about method references and how they can make the code easier to read.

Finally, we’ll talk a bit about the @FunctionalInterface annotation.
Streams
Now that we’ve covered the main concepts of functional programming in Java, it’s time to get our hands dirty and make use of what we’ve just learned.

Streams are ideal for that. We’ll learn what Streams are about and how to leverage their power. We’ll learn about the concepts of intermediate and terminal operations and the main one Java offers us.
Optionals
We’ll play a bit more with functional programming with the Optional API. Like streams, it allows us to use a functional style in our Java programs.
Comparators
Finally, we’ll see a last useful feature of Java 8, making also a nice usage of the Java functional programming possibilities: Comparator.

We’ll learn how to easily create nice and complex Comparator and how Java 8 reduces the boilerplate code a great deal.