OOP Exercises — Python & Java

A collection of object-oriented programming exercises implemented in both Python and Java, developed during my second semester of Computer Science and AI Engineering at Universidad Sergio Arboleda (Fundamentos de Software).

Each exercise includes:

• 📐 A UML class diagram — the design comes before the implementation
• ☕ A Java implementation (statically typed, extends / implements)
• 🐍 A Python implementation (ABC module simulating interfaces)
• 📝 A short README explaining the concept applied

Why design first?

Sketching the UML diagram before writing any code forces you to define the relationships between classes — inheritance, interface contracts, cardinality — before implementation details get in the way. It also makes it obvious when a language-specific implementation is inconsistent with the original design, which is exactly the kind of thing this repo is meant to demonstrate.

Concepts covered

• Abstract classes (the "is-a" relationship — shared state and behavior)
• Interfaces (the "can-do" relationship — a contract every implementer must fulfill, regardless of where it sits in the inheritance tree)
• Polymorphism (treating different concrete classes uniformly through a shared abstract type or interface)
• Encapsulation

See docs/key-concepts.md for a deeper explanation of how these ideas map between Java and Python.

Exercises

#	Domain	Classes
01	Private transportation	Transporte, Conducible, Carro, Moto, Bicicleta
02	Video game characters	Personaje, Atacante, Guerrero, Mago, Arquero
03	Streaming content	Contenido, Reproducible, Pelicula, Serie, Documental
04	Food preparation	Alimento, Preparable, Hamburguesa, Pizza, Ensalada
05	Animals	Animal, Sonoro, Perro, Gato, Vaca
06	Bank accounts	CuentaBancaria, Operable, CuentaAhorro, CuentaCorriente
07	Geometric shapes	Figura, Calculable, Circulo, Rectangulo, Triangulo
08	Electronic devices	Dispositivo, Controlable, TV, Radio, Celular
09	Professionals	Persona, Profesional, Medico, Ingeniero, Profesor
10	Public transportation	TransportePublico, Transportador, Bus, Metro, Taxi

Each exercise follows the same pattern (abstract class + interface + polymorphism) applied to a different domain, and deliberately implements a different concrete subclass in each language.

Extra: theoretical design cases

docs/theoretical-cases.md contains 10 additional design-only case studies (no code) exploring relationships that go beyond inheritance and interfaces — aggregation, composition, and association — across domains like a library system, a payment platform, and a hospital management system.

Structure

oop-exercises/
├── exercises/
│   ├── 01-transporte-privado/
│   │   ├── diagram.puml
│   │   ├── Main.java
│   │   ├── main.py
│   │   └── README.md
│   ├── 02-personajes-videojuego/
│   └── ...
└── docs/
    ├── key-concepts.md
    └── theoretical-cases.md

Stack

• Java (JDK)
• Python 3 (abc module)
• PlantUML for diagrams