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Learn Java with Projects

Learn Java with Projects

By : Dr. Seán Kennedy, Maaike van Putten
4.9 (51)
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Learn Java with Projects

Learn Java with Projects

4.9 (51)
By: Dr. Seán Kennedy, Maaike van Putten

Overview of this book

Learn Java with Projects bridges the gap between introductory Java guides and verbose, theoretical references. This book is crafted to build a strong foundation in Java programming, starting from the Java environment itself. It goes far beyond a superficial review of the topics; it demonstrates, with practical examples, why these fundamentals are crucial for developing a deep understanding of the language. You'll not only learn about classes and objects but also see how these concepts are used in practical scenarios, enhancing your ability to write clean, efficient code. The engaging projects throughout the book provide real-world applications of complex topics, ensuring you can connect theoretical knowledge with practical skills. What makes this book stand out is the expertise of its authors. Seán, a seasoned university lecturer with over 20 years of experience, brings academic rigor and real-world insights, thanks to his work with a prestigious software company. Maaike, a passionate software developer and award-winning trainer, brings hands-on experience and a love for teaching. By the end of this book, you'll not only understand Java's core concepts and the critical advanced ones, but also gain practical experience through projects that mimic real-life challenges.
Table of Contents (22 chapters)
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1
Part 1: Java Fundamentals
9
Part 2: Object-Oriented Programming
15
Part 3: Advanced Topics

Applying sealed classes

Sealed classes were introduced in Java 17. What we are going to cover here relates to classes but the same logic applies to interfaces (Chapter 10). With inheritance, you can extend from any class (or interface) using the extends keyword, unless the class is final of course.

Note

Interfaces cannot be final because their whole rationale is to be implemented.

Consider the following scenario: what if you wanted your class to be available for inheritance, but only for certain classes? In other words, you want to scope the subclasses allowed. So far, inheritance, using extends, enables every class to become a subclass, whereas final prevents a class from having subclasses.

This is where sealed classes are useful – they enable you to specify what subclasses are allowed. Just to reiterate, this also applies to interfaces, where we can specify what classes are allowed to implement the interface.

Before we look at an example, there are some new...

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