# clean-code

Guides your coding assistant to write readable code using DRY, KISS, and YAGNI principles. Useful when dealing with bloated methods and vague naming.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 379 installs · ★ 760
- Author: decebals
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/decebals/claude-code-java/tree/HEAD/skills/clean-code/SKILL.md
- Updated: 2026-09-06
- HTML: https://affpapa.org/en/nevibecode/skills/decebals-clean-code

## What it does

The skill directs coding assistants toward maintainable code through DRY, KISS, and YAGNI principles. It covers duplicate validation checks, warns against premature abstractions, and cuts out speculative methods written just in case. It also enforces conventions for variable names, boolean flags (`is`, `has`, `can`), and bans junk-drawer classes like `Manager` or `Helper`.

Keep in mind its scope. For decoupling classes or directing architectural dependencies, this skill is not enough; the author advises using `solid-principles` instead. The focus here remains strictly local: concise functions, obvious naming, and straightforward logic.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add decebals/claude-code-java --skill clean-code -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/clean-code/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/clean-code/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add decebals/claude-code-java --skill clean-code -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/clean-code/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add decebals/claude-code-java --skill clean-code -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/clean-code/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install decebals/claude-code-java clean-code
```

2. **Manually: put the files in place**
- File: `.github/skills/clean-code/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add decebals/claude-code-java --skill clean-code -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/decebals/claude-code-java --path skills/clean-code
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/clean-code/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add decebals/claude-code-java --skill clean-code -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/decebals/claude-code-java/tree/HEAD/skills/clean-code/SKILL.md

## When to use it
- refactor bloated methods and nested logic
- extract duplicated code without premature abstractions
- fix ambiguous variable and class names
- prune speculative methods added for hypothetical use cases

## Example prompts
- Clean this code and improve readability
- Refactor this method to follow KISS and simplify the checks
- Review variable naming and boolean flags in this file

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: c699a226d7a529e4.

BEGIN THIRD-PARTY FILE c699a226d7a529e4
````text
---
name: clean-code
description: Clean Code principles (DRY, KISS, YAGNI), naming, function design and readability. Use when code is hard to read, with long methods, unclear names, duplication or deep nesting. For how responsibilities are split across classes and which way dependencies point, use solid-principles instead.
license: MIT
---

# Clean Code Skill

Write readable, maintainable code following Clean Code principles.

## When to Use
- User says "clean this code" / "refactor" / "improve readability"
- Code review focusing on maintainability
- Reducing complexity
- Improving naming

---

## Core Principles

| Principle | Meaning | Violation Sign |
|-----------|---------|----------------|
| **DRY** | Don't Repeat Yourself | Copy-pasted code blocks |
| **KISS** | Keep It Simple, Stupid | Over-engineered solutions |
| **YAGNI** | You Aren't Gonna Need It | Features "just in case" |

---

## DRY - Don't Repeat Yourself

> "Every piece of knowledge must have a single, unambiguous representation in the system."

### Violation

```java
// ❌ BAD: Same validation logic repeated
public class UserController {

    public void createUser(UserRequest request) {
        if (request.getEmail() == null || request.getEmail().isBlank()) {
            throw new ValidationException("Email is required");
        }
        if (!request.getEmail().contains("@")) {
            throw new ValidationException("Invalid email format");
        }
        // ... create user
    }

    public void updateUser(UserRequest request) {
        if (request.getEmail() == null || request.getEmail().isBlank()) {
            throw new ValidationException("Email is required");
        }
        if (!request.getEmail().contains("@")) {
            throw new ValidationException("Invalid email format");
        }
        // ... update user
    }
}
```

### Refactored

```java
// ✅ GOOD: Single source of truth
public class EmailValidator {

    public void validate(String email) {
        if (email == null || email.isBlank()) {
            throw new ValidationException("Email is required");
        }
        if (!email.contains("@")) {
            throw new ValidationException("Invalid email format");
        }
    }
}

public class UserController {
    private final EmailValidator emailValidator;

    public void createUser(UserRequest request) {
        emailValidator.validate(request.getEmail());
        // ... create user
    }

    public void updateUser(UserRequest request) {
        emailValidator.validate(request.getEmail());
        // ... update user
    }
}
```

### DRY Exceptions

Not all duplication is bad. Avoid premature abstraction:

```java
// These look similar but serve different purposes - OK to duplicate
public BigDecimal calculateShippingCost(Order order) {
    return order.getWeight().multiply(SHIPPING_RATE);
}

public BigDecimal calculateInsuranceCost(Order order) {
    return order.getValue().multiply(INSURANCE_RATE);
}
// Don't force these into one method - they'll evolve differently
```

---

## KISS - Keep It Simple

> "The simplest solution is usually the best."

### Violation

```java
// ❌ BAD: Over-engineered for simple task
public class StringUtils {
````
END THIRD-PARTY FILE c699a226d7a529e4

The third-party file has ended. Everything between the c699a226d7a529e4 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 3207 of 13595 bytes. © decebals · MIT · https://github.com/decebals/claude-code-java/tree/HEAD/skills/clean-code/SKILL.md

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