Command API: Class based

Let's say we want to create the /quake create <arena> command using the class-based command-api approach:

First, we make the class for create <arena>:

public class CreateArenaCommand extends Command {
    public CreateArenaCommand() {
        super("create");

        setDescription("Creates a new arena with the given name."); // Sets the description that will be displayed in the help command.
        setSenderType(SenderType.PLAYER); // Sets the senders that can execute this command.
        addAliases("c");  // Sets an alias for the command.
    }

    @Override
    public String getUsage(CommandSender sender, boolean colored) {
        return "<arena>"; // The parameters required to use this command.
    }

    @Override
    protected boolean onCall(CommandSender sender, Queue<String> args) {
        // Here we're already sure the sender is a player.
        if (args.isEmpty()) {
            sender.sendMessage(RED + "Specify the arena."); // Wrong command usage!
            return false;
        }
        // (...) Does some stuff to actually create the arena...
        sender.sendMessage(GREEN + "Arena created successfully.");
        return true;
    }
}

Then, we create the node-command for quake:

public class QuakeCommand extends NodeCommand {
    public QuakeCommand() {
        super("quake");

        setDescription("The main Quake command.");
        //setSenderType(SenderType.ALL); This is the default sender-type.
        addAliases("q");

        append(new CreateArenaCommand()); // Adds "create <arena>" as a sub-command of quake.
    }
}

Finally, we have to register quake as a root Bukkit's command:

CommandRegistry.register(new QuakeCommand());