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

Summary

We started this chapter by examining abstract classes. An abstract class has zero or more abstract methods. However, if any method is abstract, then the class must be abstract. While an abstract class cannot be instantiated, a reference can be of an abstract type.

Before Java 8, interfaces consisted of only abstract methods (and constants). We started our discussion on interfaces at this point, where all the methods were abstract. While a class can only extend from one class, a class can implement many interfaces. This is one of the main reasons why interfaces were introduced – to be able to cast to more than one base type.

A class that implements an interface signs a “contract” to provide code for each of the abstract methods (if any) in the interface. If there is an abstract method in the interface and the concrete, non-abstract class does not provide code implementation for it, the compiler complains. Therefore, interfaces are a great way of guaranteeing...