100 Mini Java Exercises

Learning Java is not just about writing programs that work when everything goes right. It is also about knowing what to do when the user types the wrong thing, when a value does not make sense, when a file is missing, or when an operation can crash the program.
100 Mini Java Exercises: Exceptions and Validation is Book 8 in the 100 Mini Java Exercises series, a practical collection designed to help you learn Java by writing code from the very first page.
In this volume, you will work on one of the most important skills for moving beyond beginner code: building programs that are safer, more stable, and better prepared for real-world mistakes.
Across 100 progressive exercises, you will practice try-catch, concrete exception types, number validation, safer input with Scanner, empty text checks, protected objects, safer file reading, CSV line validation, and stronger console menus.
Each exercise includes a prompt, a clear goal, a complete Java solution, a step-by-step explanation, a note about validation or exceptions, and a possible improvement so you can keep practicing.
This book is ideal for students, self-taught learners, future developers, and anyone who already knows the basics of Java and wants to write code that does not break so easily.
You do not need frameworks, databases, graphical interfaces, or external libraries. You only need Java, a console, and the willingness to practice with clear, practical examples.
In this book, you will learn how to:

• Use try-catch to handle runtime errors.
• Recognize exceptions such as ArithmeticException, NumberFormatException, InputMismatchException, IOException, and more.
• Validate ages, grades, prices, percentages, and menu options.
• Read user input more safely with Scanner.
• Check empty strings, spaces, lengths, and basic text formats.
• Protect objects with constructors, setters, and validation methods.
• Read TXT and CSV files without blindly trusting their content.
• Create console menus that stay stable when the user makes a mistake.
• Build small final applications that combine validation, objects, lists, and files.