Must-do problems: Encapsulation

130 min · Beginner

In every problem the class must protect itself: fields are private, every change goes through a method that checks the rules first, and a refused command leaves the object exactly as it was. Write the class, test it from main on the samples, and run every test before opening a hint.

What you will learn

Keep every field private and change it only through methods that check the rules
Validate in setters and constructors so an object can never hold bad data
Report a refused change clearly with a boolean, a message or an exception
Protect private arrays with defensive copies and keep derived values as getters

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