Agent skill

128 Java Generics

A skill your agent uses when you need to review, improve, or refactor Java code for generics quality — including avoiding raw types, applying the PECS (Producer Extends Consumer Super) principle for…

Apache-2.0Auto-check passedDevelopment

Install 128 Java Generics

skills CLI

$ npx skills add jabrena/plinth --skill 128-java-generics -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 128-java-generics --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/128-java-generics .claude/skills/128-java-generics && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "128-java-generics" agent skill from https://github.com/jabrena/plinth/tree/main/skills/128-java-generics into .claude/skills/128-java-generics/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "128-java-generics", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/jabrena/plinth/tree/main/skills/128-java-generics

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add jabrena/plinth --skill 128-java-generics -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 128-java-generics --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/128-java-generics .agents/skills/128-java-generics && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "128-java-generics" agent skill from https://github.com/jabrena/plinth/tree/main/skills/128-java-generics into .agents/skills/128-java-generics/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "128-java-generics", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add jabrena/plinth --skill 128-java-generics -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 128-java-generics --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/128-java-generics .cursor/skills/128-java-generics && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "128-java-generics" agent skill from https://github.com/jabrena/plinth/tree/main/skills/128-java-generics into .cursor/skills/128-java-generics/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "128-java-generics", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/jabrena/plinth.git --path skills/128-java-generics

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add jabrena/plinth --skill 128-java-generics -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 128-java-generics --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/128-java-generics .gemini/skills/128-java-generics && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "128-java-generics" agent skill from https://github.com/jabrena/plinth/tree/main/skills/128-java-generics into .gemini/skills/128-java-generics/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "128-java-generics", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install jabrena/plinth 128-java-generics

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add jabrena/plinth --skill 128-java-generics -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/128-java-generics .github/skills/128-java-generics && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "128-java-generics" agent skill from https://github.com/jabrena/plinth/tree/main/skills/128-java-generics into .github/skills/128-java-generics/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "128-java-generics", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add jabrena/plinth --skill 128-java-generics -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install jabrena/plinth 128-java-generics --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/jabrena/plinth.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/128-java-generics .opencode/skills/128-java-generics && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "128-java-generics" agent skill from https://github.com/jabrena/plinth/tree/main/skills/128-java-generics into .opencode/skills/128-java-generics/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "128-java-generics", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: 128-java-generics
GitHub stars: 446
Token cost: ~956 tokens
SKILL.md length: 374 words
Files: 2 (incl. references)
Skills in repo: 124
Repo updated: Oct 7, 2026
First seen: Oct 7, 2026
Licence: Apache-2.0

At a glance

You need to review
SKILL.md covers Constraints, When to use this skill, Workflow and Reference
Calls mvn
Refactor Java code for generics quality — including avoiding raw types

What it does

128 Java Generics is an agent skill from jabrena/plinth. Use when you need to review, improve, or refactor Java code for generics quality — including avoiding raw types, applying the PECS (Producer Extends Consumer Super) principle for wildcards, using bounded type parameters, designing effective generic methods, leveraging the diamond operator, understanding type erasure implications, handling generic inheritance correctly, preventing heap pollution with @SafeVarargs, and integrating generics with modern Java features like Records, sealed types, and pattern matching…

Its SKILL.md is about 960 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files, including reference files (for example `references/128-java-generics.md`).

It sits in Development, covering Type safety and Refactoring. It works with Java. The repository describes itself as: Plinth is an AI-native engineering toolkit for modern Java enterprise SDLC, built around reusable Commands, Agents, Skills, and MCP Servers. The licence is Apache-2.0.

When your agent uses it

You need to review
Refactor Java code for generics quality — including avoiding raw types
Applying the PECS (Producer Extends Consumer Super) principle for wildcards
Using bounded type parameters

Example prompts

“/128-java-generics”

What it can do on your machine

Read from SKILL.md and the folder at commit dca88dc. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
- mvn
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

128 Java Generics loads about 956 tokens when it runs, and up to ~16k if it reads all its reference files. Until then it costs about 193 tokens; SKILL.md has 374 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~193
When it runs · the whole SKILL.md, loaded when a task matches: ~956
With references · SKILL.md plus every file in references/, read only if the agent opens them: ~16k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from jabrena/plinth at commit dca88dc, republished under its Apache-2.0 licence (© jabrena). 374 words, ~956 tokens.

Download SKILL.mdSave it as .claude/skills/128-java-generics/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.

name: 128-java-generics
description: Use when you need to review, improve, or refactor Java code for generics quality — including avoiding raw types, applying the PECS (Producer Extends Consumer Super) principle for wildcards, using bounded type parameters, designing effective generic methods, leveraging the diamond operator, understanding type erasure implications, handling generic inheritance correctly, preventing heap pollution with @SafeVarargs, and integrating generics with modern Java features like Records, sealed types, and pattern matching. This should trigger for requests such as Improve the code with Generics; Apply Generics; Refactor the code with Generics; Improve generic type safety in Java APIs; Fix raw types and unchecked casts in Java code. Part of Plinth Toolkit
license: Apache-2.0
metadata.author: Juan Antonio Breña Moral
metadata.version: 0.19.0

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

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 generics 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

Show full SKILL.md (113 more words)Show less

When to use this skill

Improve the code with Generics
Apply Generics
Refactor the code with Generics
Improve generic type safety in Java APIs
Fix raw types and unchecked casts in Java code

Workflow

Compile project before generics changes

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

Read generics reference and assess type safety

Read references/128-java-generics.md and identify raw types, unsafe casts, wildcard misuse, and API variance opportunities.

Apply generics refactorings

Implement selected generic type and API improvements while preserving behavior.

Verify with full build

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

Reference

For detailed guidance, examples, and constraints, see references/128-java-generics.md.

Files

SKILL.md and 1 other file (references) in skills/128-java-generics of jabrena/plinth.

SKILL.md
references/128-java-generics.md

Open the folder on GitHubat commit dca88dc

Compare with similar skills

128 Java Generics next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

128 Java Generics compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
128 Java Generics this skilljabrena/plinth	446	—	~956	Automated safety check: Pass	Apache-2.0	yesterday
RTK Rust Design Patternsrtk-ai/rtk	83k	—	~1.9k	Automated safety check: Pass	Apache-2.0	yesterday
Dignified Python Standardsdocling-project/docling	69k	—	~1.5k	Automated safety check: Pass	Apache-2.0	today
Nuqstrycompai/crm	11k	1 repos	~1.7k	Automated safety check: Pass	MIT	27 days ago
AST Visitor Pattern for Unionsprisma/orm	48k	—	~830	Automated safety check: Pass	Apache-2.0	today
Valgocohesivestack/valgo	508	—	~2.4k	Automated safety check: Pass	MIT	1 mo ago

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Works with

Java

Questions about 128 Java Generics

What does 128 Java Generics do?

When should I use 128 Java Generics?

128 Java Generics fits situations like: you need to review; refactor Java code for generics quality — including avoiding raw types; applying the PECS (Producer Extends Consumer Super) principle for wildcards; using bounded type parameters.

How do I install 128 Java Generics in Claude Code?

Run `npx skills add jabrena/plinth --skill 128-java-generics -a claude-code`. Or copy the skill folder (skills/128-java-generics in jabrena/plinth) into .claude/skills/128-java-generics in your project. Claude Code loads it when a task matches its description.

How do I install 128 Java Generics in Codex?

Run `npx skills add jabrena/plinth --skill 128-java-generics -a codex`. Or copy the skill folder (skills/128-java-generics in jabrena/plinth) into .agents/skills/128-java-generics in your project. Codex loads it when a task matches its description.

Can I use 128 Java Generics in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add jabrena/plinth --skill 128-java-generics -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/128-java-generics, .gemini/skills/128-java-generics, .github/skills/128-java-generics and .opencode/skills/128-java-generics in your project.

What does 128 Java Generics need to run?

Going by SKILL.md and its folder, 128 Java Generics needs the command-line tools its instructions call (mvn).

Does 128 Java Generics access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is 128 Java Generics safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does 128 Java Generics use?

128 Java Generics is published under the Apache-2.0 licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does 128 Java Generics use?

About 956 tokens (SKILL.md is roughly 3.8k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 15k tokens, read only when the agent opens those files.

What are the alternatives to 128 Java Generics?

Skills that share tags, products or a category with 128 Java Generics: RTK Rust Design Patterns (rtk-ai/rtk, 83k stars), Dignified Python Standards (docling-project/docling, 69k stars), Nuqs (trycompai/crm, 11k stars) and AST Visitor Pattern for Unions (prisma/orm, 48k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains 128 Java Generics?

jabrena (a GitHub user) maintains it in jabrena/plinth, which has 446 GitHub stars. The repository holds 124 skills in this directory. The repository was last updated on October 7, 2026.

Source: jabrena/plinth on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install 128 Java Generics

Facts

At a glance

What it does

When your agent uses it

Example prompts

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Java Generics Best Practices

Constraints

When to use this skill

Workflow

Reference

Files

Compare with similar skills

Similar skills

More from jabrena/plinth

Related

Questions about 128 Java Generics