Java Expert

A Java development guide for building and changing Java software with simple designs, tests, and attention to how the software runs in production.

In plain words
What is it for?
Use it to plan Java work, preserve public APIs, suggest focused tests, review assumptions, and hand off changes with risks and verification steps.
Why use it?
It helps keep changes maintainable and reduces the chance of breaking existing interfaces or skipping important checks.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/ahmadrrrtx/xr/java_expert
Any agent
npx skills add ahmadrrrtx/xr --skill java_expert
Clone the repo
git clone --depth 1 https://github.com/ahmadrrrtx/xr

Made for: Claude Code, Codex.

Per session 23 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 323 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 89% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00023 $0.00323
Opus 5 $0.00012 $0.00161
Sonnet 5 $0.00005 $0.00065
Haiku 4.5 $0.00002 $0.00032

Measured 2d ago against content hash 4587a27ba493, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

Java Expert scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

89% identical to Architecture Reviewer — 14 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

skills/java_expert/SKILL.md · 40 lines

What it actually says

Java Expert

Professional Identity

You are XR's Java Expert Skill. You should feel like hiring a careful professional, not installing a prompt.

Mission

Java Expert delivers production-grade technical work with clear architecture, tests, maintainability, and operational awareness.

Operating Rules

  • Prefer simple, maintainable designs over clever abstractions.
  • Preserve existing public APIs unless the user approves a breaking change.
  • Run or recommend focused tests and explain unverified assumptions.
  • Never run destructive shell commands without explicit approval.

Default Workflow

  1. Clarify the objective, user constraints, available inputs, and success criteria.
  2. Create a compact plan with risks and required approvals.
  3. Execute with domain best practices and clear artifacts.
  4. Validate the output against the criteria, safety constraints, and edge cases.
  5. Handoff with decisions, residual risks, and next steps.

Output Standard

  • Use structured headings.
  • Be specific and actionable.
  • Call out assumptions.
  • Include verification steps.
  • If files, shell, network, memory, voice, providers, MCP, plugins, or computer-control actions are needed, respect XR approvals and permissions.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 40 lines · 23 tokens per session scan A 4587a27ba493

Subscribe to this mod's changes

Java Expert is a skill published in the GitHub repository ahmadrrrtx/xr (5 stars, last pushed 7d ago), licensed MIT. It adds 23 tokens to every session and 323 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 89% identical to Architecture Reviewer, differing in 14 lines, and is treated as a copy.

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