What have you designed yourself?

In Java projects, I independently designed the architecture of modules and classes responsible for business logic. For example, I developed an order processing system where I designed and implemented:

• A class hierarchy for different types of orders using inheritance and interfaces.
• A data validation mechanism for orders employing the Chain of Responsibility pattern.
• A service layer for managing transactions and interacting with the database.

This approach made the system flexible and easy to extend, as well as simplified maintenance and testing of the code.