| Stack | Role | Year | Status |
|---|---|---|---|
| Java 17+, OOP, Maven, Gradle | Backend / Java Developer | 2025 | Open Source |
Banking System
Console-based banking system demonstrating OOP principles in Java
Banking System — Console-based banking system demonstrating OOP principles in Java is a technical case study on ancel.co.ke documenting architecture, trade-offs, and outcomes. To demonstrate clean OOP and domain modeling, I designed a small banking core where accounts, transactions, and the bank are clearly separated and easy to reason about. Ancel Ajanga wrote this case study from hands-on delivery experience in Kenya.
A simple, console-based Banking System implemented in pure Java to demonstrate core OOP principles (Encapsulation, Inheritance, Abstraction, Polymorphism). Includes customer management, savings/checking accounts, deposits, withdrawals, transfers, and transaction logs.
The Problem
Showcase solid object-oriented design and problem-solving skills without relying on external frameworks or databases.
To demonstrate clean OOP and domain modeling, I designed a small banking core where accounts, transactions, and the bank are clearly separated and easy to reason about.
The Solution
I designed an extensible domain model with an abstract Account base class and concrete Savings/Checking accounts, a Bank aggregate to manage customers/accounts, and transaction records capturing all operations.
Key Technical Terms
- Encapsulation and polymorphism:Account types hide internal state and expose a consistent interface so the Bank can treat savings and checking uniformly; that supports the goal of clear, maintainable OOP.
- Domain model / aggregate:The Bank aggregate owns customers and accounts and enforces invariants (e.g. no negative balance) so the project demonstrates how to keep business rules in one place.
- Transaction records:Every deposit, withdrawal, and transfer is recorded so we have an audit trail and can reason about correctness; that supports the goal of a credible, educational banking example.
The Impact
Clear demonstration of OOP fundamentals, clean architecture, and maintainable code suitable for technical interviews and backend design discussions.
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Outcomes
- Readable and testable code showcasing core OOP
- Lightweight console interface requiring no external services
Failure Modes & Resilience
Invalid input (e.g. negative amount): the domain model rejects or validates so we never apply invalid operations. No external I/O: the app is console-only and in-memory so there are no network or storage failures; failure handling is demonstrated through validation and clear error messages.
Outcome & Future Potential
Clear demonstration of OOP fundamentals, clean architecture, and maintainable code suitable for technical interviews and backend design discussions.
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Pure Java only
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