Use when you need to review, improve, or refactor Java code for object-oriented design quality — including applying SOLID, DRY, and YAGNI principles, improving class and interface design, fixing OOP concept misuse (encapsulation, inheritance, polymorphism), identifying and resolving code smells (God Class, Feature Envy, Data Clumps), or improving object creation patterns, method design, and exception handling. This should trigger for requests such as Review Java code for object-oriented design; Refactor Java code for object-oriented design; Improve Java code for object-oriented design; Fix OOP concept misuse in Java code. Part of cursor-rules-java project