MCPInstall

122-java-type-design

Use when you need to review, improve, or refactor Java code for type design quality — including establishing clear type hierarchies, applying consistent naming conventions, eliminating primitive obsession with domain-specific value objects, leveraging generic type parameters, creating type-safe wrappers, designing fluent interfaces, ensuring precision-appropriate numeric types (BigDecimal for financial calculations), and improving type contrast through interfaces and method signature alignment. This should trigger for requests such as Review Java code for type design; Improve type design in Java code; Fix primitive obsession in Java code; Create value objects in Java code. Part of Plinth Toolkit

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Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/jabrena/plinth --skill 122-java-type-design
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads 122-java-type-design automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

Type Design Thinking in Java

Review and improve Java code using comprehensive type design principles that apply typography concepts to code structure and organization for maximum clarity and maintainability.

What is covered in this Skill?

  • Clear type hierarchies: nested static classes, logical structure
  • Consistent naming conventions: domain-driven patterns, uniform interface/implementation naming
  • Strategic whitespace for readability
  • Type-safe wrappers: value objects replacing primitive obsession (EmailAddress, Money)
  • Generic type parameters: flexible reusable types, bounded parameters
  • Domain-specific fluent interfaces: builder pattern, method chaining
  • Type weights: conceptual importance — core domain vs supporting vs utility
  • Type contrast through interfaces: contract vs implementation separation
  • Aligned method signatures: consistent parameter and return types across related classes
  • Self-documenting code: clear descriptive names
  • BigDecimal for precision-sensitive calculations (financial/monetary operations)
  • Strategic type selection: Optional, Set vs List, interfaces over concrete types

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 type design 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
  • EDGE CASE: If request scope is ambiguous, stop and ask a clarifying question before applying changes
  • EDGE CASE: If required inputs, files, or tooling are missing, report what is missing and ask whether to proceed with setup guidance

When to use this skill

  • Review Java code for type design
  • Improve type design in Java code
  • Fix primitive obsession in Java code
  • Create value objects in Java code
  • Create type hierarchies in Java code
  • Create fluent interfaces in Java code

Workflow

  1. Compile project before type-design changes

Run ./mvnw compile or mvn compile and stop immediately if compilation fails.

  1. Read type-design reference and inspect code

Read references/122-java-type-design.md and identify type hierarchy, naming, and value-object improvements.

  1. Apply type-design refactorings

Implement selected type-safety and readability improvements based on applicable patterns.

  1. Verify with full build

Run ./mvnw clean verify or mvn clean verify after applying improvements.

Reference

For detailed guidance, examples, and constraints, see references/122-java-type-design.md.

FAQ

What does the 122-java-type-design skill do?

Use when you need to review, improve, or refactor Java code for type design quality — including establishing clear type hierarchies, applying consistent naming conventions, eliminating primitive obsession with domain-specific value objects, leveraging generic type parameters, creating type-safe wrappers, designing fluent interfaces, ensuring precision-appropriate numeric types (BigDecimal for financial calculations), and improving type contrast through interfaces and method signature alignment. This should trigger for requests such as Review Java code for type design; Improve type design in Java code; Fix primitive obsession in Java code; Create value objects in Java code. Part of Plinth Toolkit

How do I install 122-java-type-design?

Run npx skills add https://github.com/jabrena/plinth --skill 122-java-type-design in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/122-java-type-design/ (personal) or .claude/skills/122-java-type-design/ (project).

Which AI agents can use 122-java-type-design?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is 122-java-type-design safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains 122-java-type-design?

It is published by jabrena in jabrena/plinth. It has 397 recorded installs.

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