git:20260719.d6bc5a1 to v0.1.0

---

name: coding-java

description: Java naming conventions, exception hierarchy, import patterns, and quality overrides for ECHO Protocol.

---

# Java Coding Standards

<!-- Load this when protocol.config.yaml has language: "java" -->

## Naming Conventions

| Element | Convention | Example |

|---------|-----------|---------|

| Classes | PascalCase | `UserProfile`, `GameState` |

| Interfaces | PascalCase | `Serializable`, `Renderable` |

| Methods | camelCase | `calculateDistance`, `spawnUnit` |

| Variables | camelCase | `playerCount`, `isValid` |

| Constants | UPPER_SNAKE_CASE | `MAX_PLAYERS`, `TILE_SIZE` |

| Enums | PascalCase (class), UPPER_SNAKE_CASE (values) | `TileType.GRASSLAND` |

| Packages | lowercase, reversed domain | `com.example.gameengine` |

| Files | PascalCase.java (match class name) | `UserProfile.java` |

## Patterns

### Error Handling

- Use custom exception hierarchy extending `Exception`

- Catch specific exceptions, never bare `Exception`

- Use try-with-resources for AutoCloseable

- Log at catch points with context

### Concurrency

- Prefer `ExecutorService` over raw threads

- Use `synchronized` or `ReentrantLock` for shared state

- Immutable objects preferred over synchronization

- Use `CompletableFuture` for async composition

### Imports

- Group: java → javax → external → internal

- No wildcard imports

- Use IDE auto-import management

## File Structure

```text

src/main/java/com/example/

├── Application.java # Entry point

├── config/

│ └── AppConfig.java # Configuration

├── exception/

│ └── AppException.java # Custom exceptions

├── model/

│ └── [Domain].java # Data classes

├── service/

│ └── [Domain]Service.java # Business logic

src/test/java/

└── [Mirror structure]

```

## Anti-Patterns to Flag

- [ ] Bare `catch (Exception e)`

- [ ] Mutable static fields

- [ ] God classes (>300 lines)

- [ ] Deep inheritance hierarchies (>3 levels)

- [ ] `null` returns instead of Optional

- [ ] Magic numbers (extract to constants)

## Quality Overrides

These override the defaults in `protocol.config.yaml` when Java is the configured language.

| Setting | Default | Java Override | Reason |

|---------|---------|---------------|--------|

| `max_file_lines` | 300 | 350 | Java boilerplate (imports, generics) adds lines |

| `max_function_lines` | 50 | 40 | Java methods should be shorter due to verbosity |

| `max_line_length` | 100 | 120 | Standard Java convention |