# java

> Handles Java 11 development, L2J package structure, singleton patterns, and thread-safe coding conventions.
Use when: Writing new classes, managers, handlers, or modifying existing Java code in the L2J codebase.

- Author: valeriybaranyshyn-pixel
- Repository: valeriybaranyshyn-pixel/Tales-of-Aden
- Version: 20260202145225
- Stars: 0
- Forks: 0
- Last Updated: 2026-02-06
- Source: https://github.com/valeriybaranyshyn-pixel/Tales-of-Aden
- Web: https://mule.run/skillshub/@@valeriybaranyshyn-pixel/Tales-of-Aden~java:20260202145225

---

---
name: java
description: |
  Handles Java 11 development, L2J package structure, singleton patterns, and thread-safe coding conventions.
  Use when: Writing new classes, managers, handlers, or modifying existing Java code in the L2J codebase.
allowed-tools: Read, Edit, Write, Glob, Grep, Bash, mcp__context7__resolve-library-id, mcp__context7__query-docs
---

# Java Skill

Java 11 development for the Tales of Aden L2J server. This codebase follows L2J conventions: underscore-prefixed private fields, singleton managers, handler interfaces, and intention-based AI patterns. All code targets Java 11—do not use features from newer versions.

## Quick Start

### Singleton Manager Pattern

```java
public class YourManager {
    private static final Logger _log = Logger.getLogger(YourManager.class.getName());

    private static class SingletonHolder {
        protected static final YourManager _instance = new YourManager();
    }

    public static YourManager getInstance() {
        return SingletonHolder._instance;
    }

    private YourManager() {
        // initialization
    }
}
```

### Handler Implementation

```java
public class YourHandler implements IAdminCommandHandler {
    private static final String[] ADMIN_COMMANDS = {
        "admin_your_command",
        "admin_your_other_command"
    };

    @Override
    public boolean useAdminCommand(String command, Player activeChar) {
        if (command.startsWith("admin_your_command")) {
            // handle command
        }
        return true;
    }

    @Override
    public String[] getAdminCommandList() {
        return ADMIN_COMMANDS;
    }
}
```

## Key Concepts

| Concept | Convention | Example |
|---------|------------|---------|
| Private fields | Underscore prefix | `_log`, `_actor`, `_thinking` |
| Constants | SCREAMING_SNAKE | `AVOID_RADIUS`, `MAX_DELAY` |
| Config keys | PascalCase | `Config.ENABLE_AIO_SYSTEM` |
| Packages | lowercase | `net.sf.l2j.event.tvt` |
| Entity classes | L2 prefix | `L2Summon`, `L2Skill` |

## Common Patterns

### Database Access with Try-With-Resources

**When:** Any database operation

```java
try (Connection con = ConnectionPool.getConnection();
     PreparedStatement ps = con.prepareStatement("SELECT * FROM table WHERE id = ?")) {
    ps.setInt(1, id);
    try (ResultSet rs = ps.executeQuery()) {
        while (rs.next()) {
            // process results
        }
    }
} catch (SQLException e) {
    _log.warning("Failed to load data: " + e.getMessage());
}
```

### Scheduled Tasks

**When:** Periodic operations (events, cleanup, updates)

```java
private ScheduledFuture<?> _task;

public void startTask() {
    _task = ThreadPool.scheduleAtFixedRate(() -> {
        // periodic work
    }, 1000, 60000); // initial delay, period (ms)
}

public synchronized void stopTask() {
    if (_task != null) {
        _task.cancel(false);
        _task = null;
    }
}
```

### Thread-Safe State Flags

**When:** AI or concurrent operations

```java
private volatile boolean _thinking;

@Override
protected void onEvtThink() {
    if (_thinking || _actor.isCastingNow())
        return;

    _thinking = true;
    try {
        // process AI logic
    } finally {
        _thinking = false;
    }
}
```

## See Also

- [patterns](references/patterns.md) - Singleton, handler, AI patterns
- [types](references/types.md) - Collections, concurrency, logging
- [modules](references/modules.md) - Package organization, manager registration
- [errors](references/errors.md) - Exception handling, database errors

## Related Skills

- See the **ant** skill for build configuration
- See the **mariadb** skill for database queries
- See the **l2j-gameserver** skill for game server specifics
- See the **ai-system** skill for AI implementation
- See the **item-handlers** skill for item handler patterns
- See the **pvp-events** skill for event manager patterns

## Documentation Resources

> Fetch latest Java 11 documentation with Context7.

**How to use Context7:**
1. Use `mcp__context7__resolve-library-id` to search for "java 11"
2. **Prefer website documentation** (IDs starting with `/websites/`) over source code repositories
3. Query with `mcp__context7__query-docs` using the resolved library ID

**Recommended Queries:**
- "java concurrency patterns"
- "java try with resources"
- "java logging best practices"