# Java Review

> Reviews Java code for bugs, naming issues, code smells, and version-appropriate idioms. Use when user asks to "review this code", "check my Java", "look at this class", "find issues in", "code review", "what's wrong with this", or "review this file".

- Skill: `ducpm2303/java-review` (Agent Skill)
- Install (CLI): `npx skillmds@latest add ducpm2303/java-review`
- Raw SKILL.md: https://api.skillmd.com/api/skills/ducpm2303/java-review/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ducpm2303 (https://skillmd.com/u/ducpm2303)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/ducpm2303/java-review

---


Review the Java code I've selected or provided. Follow these steps:

## Step 1 — Detect Java version
Check the project for `pom.xml` (look for `<java.version>` or `<maven.compiler.source>`) or `build.gradle` (look for `sourceCompatibility`). If not found, ask: "What Java version are you targeting? (8, 11, 17, 21, or other)"

## Step 2 — Review for bugs and correctness
- **Null safety:** flag unguarded dereferences; suggest `Optional<T>` (Java 8+) for values that may be absent
- **Resource leaks:** flag unclosed `InputStream`, `Connection`, `PreparedStatement`; suggest try-with-resources
- **equals/hashCode:** if one is overridden without the other, flag it
- **Collection mutation:** flag modification of a collection while iterating over it
- **Thread safety:** flag shared mutable fields accessed from multiple threads without synchronization
- **Off-by-one:** review loop bounds and index access

## Step 3 — Review naming and style
- Classes/interfaces: must be `PascalCase`
- Methods/variables: must be `camelCase`
- Constants (static final): must be `SCREAMING_SNAKE_CASE`
- Flag single-letter variable names outside of loop counters (`i`, `j`, `k`)
- Flag abbreviations that reduce clarity (e.g., `usr` → `user`, `mgr` → `manager`)

## Step 4 — Review Java idioms (version-aware)
For each suggestion involving a version-gated feature, state: "Requires Java X+"
- Java 8+: suggest streams/lambdas over verbose imperative loops where clarity improves
- Java 8+: suggest try-with-resources for `Closeable` resources
- Java 10+: suggest `var` where the type is obvious from the right-hand side
- Java 16+: suggest records for classes that are pure data holders with no behaviour
- Java 17+: suggest sealed classes for fixed hierarchies; pattern matching for `instanceof` chains

## Step 5 — Review code smells
- Methods longer than 20 lines: suggest extracting to named helper methods
- Classes with more than one clear responsibility: suggest splitting
- Magic numbers/strings: suggest named constants
- Deep nesting (more than 3 levels): suggest early returns or extraction

## Output format
Respond with:
1. **Summary** — 1–2 sentences overall assessment
2. **Issues** — grouped by severity:
   - 🔴 **Critical** (bugs, resource leaks, thread safety)
   - 🟡 **Warning** (naming, missing equals/hashCode, raw types)
   - 🔵 **Suggestion** (idiom improvements, version-gated enhancements)
3. **Strengths** — what is done well (at least one observation)

Be concise. Each issue: one sentence description + one-line fix example.

## Next Steps
After completing this review, offer these follow-up actions based on findings:
- If structural issues found (long methods, god classes) → suggest running `/java-refactor`
- If missing or inadequate tests found → suggest running `/java-test`
- If security issues found (SQL concat, hardcoded secrets, weak crypto) → suggest delegating to the `java-security-reviewer` agent
- If performance issues found (N+1, unbounded queries, String concatenation in loops) → suggest delegating to the `java-performance-reviewer` agent
- If Javadoc is missing on public API → suggest running `/java-docs`