Worked on the Recruiting-Your-Club/ryc repository to enhance the Club domain model by focusing on immutability and safer object initialization. Applied the Builder Pattern and Java’s object-oriented principles to refactor the codebase, introducing final fields and removing mutable methods to reduce runtime errors. Utilized @Builder.Default to ensure collections within the Club model are initialized by default, preventing NullPointerExceptions and improving robustness. These changes were implemented through incremental, traceable commits, prioritizing maintainability and minimal behavioral impact. The work demonstrated a methodical approach to refactoring, leveraging Java and refactoring skills to enable safer future development and easier maintenance.