Developed foundational domain models for both a Library management system and a Banking system within the next-engineer/next-java-exercise repository, focusing on clean architecture and modular design. The work included implementing core Java classes for entities such as Book, Member, Library, and Account, supporting workflows like borrowing, returning, deposits, and withdrawals. Emphasized object-oriented programming principles and established a project structure that facilitates rapid feature expansion and straightforward unit testing. Demonstrated disciplined Git practices through dedicated feature branching and assignment-based commits. The codebase now provides a clear foundation for future enhancements, with well-defined APIs and maintainable Java code supporting domain-driven development.