121 Java Object Oriented Design

This is a refactoring aid that runs your Java code through an OOD quality check before making any changes. It enforces compilation as a safety gate, then applies SOLID principles, fixes code smells like God Class and Feature Envy, and improves patterns around object creation, method signatures, and exception handling. The workflow is deliberate: compile first, read the reference guide for good and bad patterns, apply focused refactorings, then verify with a full Maven build. It's built for systematic cleanup work rather than greenfield development, and the hard stop on compilation failures keeps you from digging deeper holes. Part of the cursor-rules-java project by Juan Antonio Breña Moral.

skills.sh installs: 153
GitHub stars: 393
last updated: Jun 3, 2026

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Install

$ npx -y skills add jabrena/cursor-rules-java --skill 121-java-object-oriented-design --agent claude-code

Installs into .claude/skills of the current project.

Files

Java Object-Oriented Design Guidelines

Review and improve Java code using focused object-oriented design references selected after assessing the request and affected code.

What is covered in this Skill?

Fundamental design principles (SOLID, DRY, YAGNI)
Class and interface design: composition over inheritance, immutability, accessibility minimization, accessor methods
Core OOP concepts: encapsulation, inheritance, polymorphism
Object creation patterns: static factory methods, Builder, Singleton, dependency injection, avoiding unnecessary objects
OOD code smells: God Class, Feature Envy, Inappropriate Intimacy, Refused Bequest, Shotgun Surgery, Data Clumps
Method design: parameter validation, defensive copies, careful signatures, empty collections over nulls, Optional usage
Exception handling: checked vs. runtime exceptions, standard exceptions, failure-capture messages, no silent ignoring

Scope: Classify the applicable OOD concerns first, then load only the focused references needed for those concerns. Load multiple references when a refactoring crosses concern boundaries.