Subcommands

I don't know how to make subcommands like /command help .
What is the code for that?

/Carlgo11

 

Code:

public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args) {
    if(args.length<=0) {
        args = new String[]{ "help" };
    }
    if(args[0].equalsIgnoreCase("help")) {
        // Print Help Here
        return true;
    }
    if(args[0].equalsIgnoreCase("justinbieberforever")) {
        if(sender instanceof Player) {
            Player player = (Player) sender;
            for(int i = 0; i < 10; i++) player.getWorld().spawnCreature(player.getLocation(), EntityType.CREEPER);
        }
        sender.sendMessage(">=(");
        return true;
    }
    sender.sendMessage("Unrecognized Command");
    return false;
}