100 Java Mini Exercises

Learn object-oriented programming in Java through 100 clear, practical, and progressive mini exercises.

This fifth volume in the 100 Java Mini Exercises series is dedicated to one of the most important steps for anyone who wants to truly understand Java: classes, objects, attributes, constructors, encapsulation, and small object-oriented systems.

If you already know variables, conditionals, loops, arrays, strings, and methods, this book will help you take the next step: stop writing programs with loose data and start organizing your code around real-world entities.

Throughout the book, you will learn how to create classes such as:

Person, Student, Product, Book, BankAccount, Employee, Customer, Order, Invoice, Reservation, Course, and many more.

Each exercise is designed to help you understand one specific concept without unnecessary theory. You will begin by creating simple classes. Then you will add instance methods, constructors, private attributes, getters, setters, validations, the this keyword, objects inside other objects, and arrays of objects.

The goal is to help you understand object-oriented programming step by step, with everyday examples and easy-to-follow Java code.

In this book, you will learn how to:

• create your own classes in Java;
• create objects using new;
• work with attributes and instance methods;
• use constructors to initialize objects;
• protect data with private;
• use getters and setters;
• validate data inside a class;
• understand the this keyword;
• create objects related to other objects;
• work with arrays of objects;
• build small object-oriented console systems.

This is not a heavy theory book. It is a hands-on practice book.

Each exercise includes a statement, a goal, a complete Java solution, a step-by-step explanation, an object-oriented programming note, and a possible improvement.

If you want to understand OOP in Java without getting lost in complicated explanations, this book will guide you from your first class to your first small object-oriented systems.