Modern Java Recipes

Chapter 1. The Basics

The biggest change in Java 8 is the addition of concepts from functional programming to the language. Specifically, the language added lambda expressions, method references, and streams.

If you haven’t used the new functional features yet, you’ll probably be surprised by how different your code will look from previous Java versions. The changes in Java 8 represent the biggest changes to the language ever. In many ways, it feels like you’re learning a completely new language.

The question then becomes: Why do this? Why make such drastic changes to a language that’s already twenty years old and plans to maintain backward compatibility? Why make such dramatic revisions to a language that has been, by all accounts, extremely successful? Why switch to a functional paradigm after all these years of being one of the most successful object-oriented languages ever?

The answer is that the software development world has changed, so languages that want to be successful in the future need to adapt as well. Back in the mid-’90s, when Java was shiny and new, Moore’s law¹ was still fully in force. All you had to do was wait a couple of years and your computer would double in speed.

Today’s hardware no longer relies on increasing chip density for speed. Instead, even most phones have multiple cores, which means software needs to be written expecting to be run in a multiprocessor environment. Functional programming, with its emphasis on “pure” functions (that return the same ...