128 Java Generics

This is a comprehensive refactoring assistant for cleaning up Java generics across your codebase. It walks you through eliminating raw types, applying PECS (Producer Extends Consumer Super) for wildcards, fixing unsafe casts, and integrating generics with modern Java features like Records and sealed types. The workflow is strict: it forces a compile check before touching anything, then guides you through the reference material with good/bad code examples, then verifies everything still builds. Honestly, the mandatory compile gates are smart because generics refactoring can spiral into type errors fast. Best used when you have legacy code that compiles but is littered with warnings, or when you're tightening up API boundaries and want proper variance.

skills.sh installs: 135
GitHub stars: 393
last updated: Jun 3, 2026

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Install

$ npx -y skills add jabrena/cursor-rules-java --skill 128-java-generics --agent claude-code

Installs into .claude/skills of the current project.

Files

Java Generics Best Practices

Review and improve Java code using comprehensive generics best practices that enforce compile-time type safety and enable flexible, reusable APIs.

What is covered in this Skill?

Type safety: avoiding raw types, eliminating unsafe casts
Code reusability: generic methods and types for multiple type contexts
PECS wildcards: ? extends for producers, ? super for consumers
Diamond operator for type inference
Type erasure awareness: type tokens, factory patterns, array creation
Generic inheritance and variance: invariance, covariance, contravariance
@SafeVarargs for heap pollution prevention
Wildcard capture helpers, self-bounded generics (CRTP) for fluent builders
Proper wildcard API design: Comparator<? super T>, Function<? super T, ? extends R>
Arrays-vs-generics covariance pitfalls, serialization with TypeReference/TypeToken
Generic naming conventions (T, E, K/V, ?), typesafe heterogeneous containers
Integration with Records, sealed types, and pattern matching