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

Explaining varargs

Consider the following situation: you want to call a method, m1, but the number of arguments may vary. Do you overload the method with each version of the method taking in one extra parameter? For example, assuming the argument types are of the String type, do you overload m1 when each new version takes in an extra String parameter? In this case, you would have to code m1(String), m1(String, String), m1(String, String, String), and so forth. This is not scalable.

This is where varargs comes in. varargs is a very flexible language feature in Java, specifically provided for this use case. The syntax is that the type name is followed by an ellipsis (three dots). Figure 7.10 shows varargs in action:

Figure 7.10 – varargs example

Figure 7.10 – varargs example

In this figure, on line 10, m1(int… ) defines a method signature for the m1 method, defining 0 or more int parameters. This is quite different from String[] defined on line 4 for main. In effect...