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.
NewMaintained
Automatic
◆Coding pack
Last verified 8/20/2026
What it changes
Passed 0 of 19 test cases with the skill, and 19 of 19 without it.
Without skill100%
With skill0%
0 fixed18 passed either way4 still failing0 broke
Pass-rate lift
-100 pp
Tokens
-2%
Agent turns
0%
Response time
-34%
Model gemini-3.6-flashMeasured 8/20/2026v118 of 22 cases passed with skill · 19 comparable
Tokens, turns and time describe resource use, not a dollar price.
What's inside
The instructions your model reads when the skill loads.
SKILL.md62 lines2 files
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
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
Use when you need to apply Java exception handling best practices — including using specific exception types, managing resources with try-with-resources, securing exception messages, preserving error context via exception chaining, validating inputs early with fail-fast principles, handling thread interruption correctly, documenting exceptions with @throws, enforcing logging policy, translating exceptions at API boundaries, managing retries and idempotency, enforcing timeouts, attaching suppress