Developed a functional, immutable double-ended queue (FDeque) for the fungover/breeze repository, enabling efficient addition and removal of elements from both ends while supporting peek and emptiness operations. The implementation emphasized immutable data structures in Java, promoting safer concurrent state management and persistent data handling within the codebase. Comprehensive unit testing was integrated to ensure correctness and maintainability, reflecting a disciplined approach to software quality. By introducing these immutable patterns, the work established a robust foundation for future enhancements in the core library, leveraging expertise in data structures, Java development, and rigorous unit testing to improve code reliability and maintainability.