Java Object-Oriented Design Guidelines
Review and improve Java code using comprehensive object-oriented design guidelines and refactoring practices.
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: The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.
Constraints
Before applying any OOD changes, ensure the project compiles. If compilation fails, stop immediately — do not proceed until resolved. After applying improvements, run full verification.
- MANDATORY: Run
./mvnw compile or mvn compile before applying any change
- SAFETY: If compilation fails, stop immediately and do not proceed — compilation failure is a blocking condition
- VERIFY: Run
./mvnw clean verify or mvn clean verify after applying improvements
- BEFORE APPLYING: Read the reference for detailed examples, good/bad patterns, and constraints
When to use this skill
- 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
- Identify and resolve code smells in Java code
- Improve object creation patterns in Java code
- Improve method design in Java code
- Improve exception handling in Java code
Reference
For detailed guidance, examples, and constraints, see references/121-java-object-oriented-design.md.
1---2name: 121-java-object-oriented-design3description: 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. Part of the skills-for-java project4license: Apache-2.05---6# Java Object-Oriented Design Guidelines78Review and improve Java code using comprehensive object-oriented design guidelines and refactoring practices.910**What is covered in this Skill?**1112- Fundamental design principles (SOLID, DRY, YAGNI)13- Class and interface design: composition over inheritance, immutability, accessibility minimization, accessor methods14- Core OOP concepts: encapsulation, inheritance, polymorphism15- Object creation patterns: static factory methods, Builder, Singleton, dependency injection, avoiding unnecessary objects16- OOD code smells: God Class, Feature Envy, Inappropriate Intimacy, Refused Bequest, Shotgun Surgery, Data Clumps17- Method design: parameter validation, defensive copies, careful signatures, empty collections over nulls, Optional usage18- Exception handling: checked vs. runtime exceptions, standard exceptions, failure-capture messages, no silent ignoring1920**Scope:** The reference is organized by examples (good/bad code patterns) for each core area. Apply recommendations based on applicable examples.2122## Constraints2324Before applying any OOD changes, ensure the project compiles. If compilation fails, stop immediately — do not proceed until resolved. After applying improvements, run full verification.2526- **MANDATORY**: Run `./mvnw compile` or `mvn compile` before applying any change27- **SAFETY**: If compilation fails, stop immediately and do not proceed — compilation failure is a blocking condition28- **VERIFY**: Run `./mvnw clean verify` or `mvn clean verify` after applying improvements29- **BEFORE APPLYING**: Read the reference for detailed examples, good/bad patterns, and constraints3031## When to use this skill3233- Review Java code for object-oriented design34- Refactor Java code for object-oriented design35- Improve Java code for object-oriented design36- Fix OOP concept misuse in Java code37- Identify and resolve code smells in Java code38- Improve object creation patterns in Java code39- Improve method design in Java code40- Improve exception handling in Java code4142## Reference4344For detailed guidance, examples, and constraints, see [references/121-java-object-oriented-design.md](references/121-java-object-oriented-design.md).
jabrena