java-code-review

Java Code Review Skill

Systematic code review checklist for Java projects.

When to Use

• User says "review this code" / "check this PR" / "code review"
• Before merging a PR
• After implementing a feature

Review Strategy

1. Quick scan - Understand intent, identify scope
2. Checklist pass - Go through each category below
3. Summary - List findings by severity (Critical → Minor)

Output Format

## Code Review: [file/feature name]

### Critical
- [Issue description + line reference + suggestion]

### Improvements
- [Suggestion + rationale]

### Minor/Style
- [Nitpicks, optional improvements]

### Good Practices Observed
- [Positive feedback - important for morale]

---

Review Checklist

1. Null Safety

Check for:

// ❌ NPE risk
String name = user.getName().toUpperCase();

// ✅ Safe
String name = Optional.ofNullable(user.getName())
    .map(String::toUpperCase)
    .orElse("");

// ✅ Also safe (early return)
if (user.getName() == null) {
    return "";
}
return user.getName().toUpperCase();

Flags:

• Chained method calls without null checks
• Missing @Nullable / @NonNull annotations on public APIs
• Optional.get() without isPresent() check
• Returning null from methods that could return Optional or empty collection

Suggest:

• Use Optional for return types that may be absent
• Use Objects.requireNonNull() for constructor/method params
• Return empty collections instead of null: Collections.emptyList()

2. Exception Handling

Check for:

// ❌ Swallowing exceptions
try {
    process();
} catch (Exception e) {
    // silently ignored
}

// ❌ Catching too broad
catch (Exception e) { }
catch (Throwable t) { }

// ❌ Losing stack trace
catch (IOException e) {
    throw new RuntimeException(e.getMessage());
}

// ✅ Proper handling
catch (IOException e) {
    log.error("Failed to process file: {}", filename, e);
    throw new ProcessingException("File processing failed", e);
}