Book Image

Learn Java with Projects

By : Dr. Seán Kennedy, Maaike van Putten
5 (3)
Book Image

Learn Java with Projects

5 (3)
By: Dr. Seán Kennedy, Maaike van Putten

Overview of this book

Learn Java with Projects stands out in the world of Java guides; while some books skim the surface and others get lost in too much detail, this one finds a nice middle ground. You’ll begin by exploring the fundamentals of Java, from its primitive data types through to loops and arrays. Next, you’ll move on to object-oriented programming (OOP), where you’ll get to grips with key topics such as classes, objects, encapsulation, inheritance, polymorphism, interfaces, and more. The chapters are designed in a way that focuses on topics that really matter in real-life work situations. No extra fluff here, so that you get more time to spend on the basics and form a solid foundation. As you make progress, you’ll learn advanced topics including generics, collections, lambda expressions, streams and concurrency. This book doesn't just talk about theory—it shows you how things work with little projects, which eventually add up to one big project that brings it all together. By the end of this Java book, you’ll have sound practical knowledge of Java and a helpful guide to walk you through the important parts of Java.
Table of Contents (22 chapters)
1
Part 1: Java Fundamentals
9
Part 2: Object-Oriented Programming
15
Part 3: Advanced Topics

Streams – Fundamentals

In Chapter 14, we learned about lambda expressions. Lambda expressions enable us to write more concise code. Be aware, however, that the compiler is, in the background, inserting the code we omit. For that to work, the compiler must have no decisions to make. This is where “functional interfaces” come into play. A functional interface is an interface with just one abstract method; this is known as the “functional method.” Lambda expressions can only be used with functional interfaces.

We saw that if a local variable is used in a lambda expression, that variable must be final or “effectively final.” This keeps both views (method and lambda) of the variable’s value in sync. In other words, both the method and the lambda have the same value for the variable at all times.

We also examined the more popular functional interfaces in the API, namely, Predicate, BiPredicate, Supplier, Consumer, BiConsumer,...