121-java-object-oriented-design

121-java-object-oriented-design is a skill for Claude Code, Codex from jabrena/cursor-rules-examples. It costs 97 tokens per session (590 once invoked), scanned A, original, Apache-2.0.

A guide for reviewing and improving Java object-oriented design, the way code organizes data and behavior into classes and interfaces. It covers common design principles, patterns, and code smells, which are recurring signs of difficult-to-maintain code.

In plain words
What is it for?
Use it to review or refactor Java classes, interfaces, object creation, methods, exceptions, and common design problems, provided the project already compiles.
Why use it?
It helps identify poor class boundaries, unnecessary complexity, misuse of inheritance, weak error handling, and other design problems before refactoring.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

Good fit Use it to review or refactor Java classes, interfaces, object creation, methods, exceptions, and common design problems, provided the project already compiles.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/jabrena/cursor-rules-examples/121-java-object-oriented-design
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.

Any agent
npx skills add jabrena/cursor-rules-examples --skill 121-java-object-oriented-design
Clone the repo
git clone --depth 1 https://github.com/jabrena/cursor-rules-examples

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for 121-java-object-oriented-design

README.md
[![agentmods](https://agentmods.dev/badge/skills/jabrena/cursor-rules-examples/121-java-object-oriented-design/github.svg)](https://agentmods.dev/skills/jabrena/cursor-rules-examples/121-java-object-oriented-design)
Your own site
<a href="https://agentmods.dev/skills/jabrena/cursor-rules-examples/121-java-object-oriented-design"><img src="https://agentmods.dev/badge/skills/jabrena/cursor-rules-examples/121-java-object-oriented-design/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for 121-java-object-oriented-design

Your own site · 80×15
<a href="https://agentmods.dev/skills/jabrena/cursor-rules-examples/121-java-object-oriented-design"><img src="https://agentmods.dev/badge/skills/jabrena/cursor-rules-examples/121-java-object-oriented-design.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 97 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 590 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found 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 5.1 $0.00097 $0.00590
Opus 5.5 $0.00039 $0.00236
Sonnet 5.5 $0.00019 $0.00118
Haiku 4.5 $0.00010 $0.00059

Measured 1mo ago against content hash 280d79034b12, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

121-java-object-oriented-design 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 1mo 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.

.agents/skills/121-java-object-oriented-design/SKILL.md · 48 lines

How it starts

The opening of the file, as written. The whole thing — 48 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Java Object-Oriented Design Guidelines

Review and improve Java code using comprehensive object-oriented design guidelines and refactoring practices.

What is covered in this Skill?

  • Fundamental design principles (SOLID, DRY, YAGNI)
  • Class and interface design: composition over inheritance, immutability, accessibility minimization, accessor methods
  • Core OOP concepts: encapsulation, inheritance, polymorphism
  • Object creation patterns: static factory methods, Builder, Singleton, dependency injection, avoiding unnecessary objects
  • OOD code smells: God Class, Feature Envy, Inappropriate Intimacy, Refused Bequest, Shotgun Surgery, Data Clumps
  • Method design: parameter validation, defensive copies, careful signatures, empty collections over nulls, Optional usage
  • Exception handling: checked vs. runtime exceptions, standard exceptions, failure-capture messages, no silent ignoring

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 OOD 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

When to use this skill

  • Review Java code for object-oriented design
  • Refactor Java code for object-oriented design
  • Improve Java code for object-oriented design
  • Fix OOP concept misuse in Java code
  • Identify and resolve code smells in Java code
  • Improve object creation patterns in Java code
  • Improve method design in Java code
  • Improve exception handling in Java code

Read the full file on GitHub · 48 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 1mo ago First seen · 48 lines · 97 tokens per session scan A 280d79034b12

Subscribe to this mod's changes

121-java-object-oriented-design is a skill published in the GitHub repository jabrena/cursor-rules-examples (2 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 97 tokens to every session and 590 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Related

Other skills, from other repositories

code-review-excellence

Master effective code review practices to provide constructive feedback, catch bugs early, and foster knowledge sharing while maintaining team morale. Use when reviewing pull requests, establishing review standards, or mentoring developers.

wshobson/agents · 42 tokens

multi-reviewer-patterns

Coordinate parallel code reviews across multiple quality dimensions with finding deduplication, severity calibration, and consolidated reporting. Use this skill when organizing multi-reviewer code reviews, calibrating finding severity, or consolidating review results.

wshobson/agents · 49 tokens

temporal-python-testing

Test Temporal workflows with pytest, time-skipping, and mocking strategies. Covers unit testing, integration testing, replay testing, and local development setup. Use when implementing Temporal workflow tests or debugging test failures.

wshobson/agents · 45 tokens

solid-principles

SOLID principles checklist with Java examples. Use when a class has too many responsibilities, an abstraction leaks, or a dependency points the wrong way, and when the user asks about Single Responsibility, Open/Closed, Liskov, Interface Segregation or Dependency Inversion. For naming, duplication and method length…

decebals/claude-code-java · 73 tokens

814-regulations-iso-25010

Use when reviewing, designing, or modifying Java enterprise systems and need a structured, repeatable ISO/IEC 25010:2023 quality-attribute review covering Functional Suitability, Performance Efficiency, Compatibility, Interaction Capability, Reliability, Security, Maintainability, Flexibility, and Safety, producing an…

jabrena/plinth · 83 tokens

121-java-object-oriented-design

Use when reviewing, improving, or refactoring Java object-oriented design, including applying SOLID, DRY, or YAGNI; improving classes and interfaces; correcting encapsulation, inheritance, or polymorphism; resolving God Class, Feature Envy, or Data Clumps; and improving object creation, methods, or exception…

jabrena/plinth · 107 tokens