Nickname

public static HashMap<Player, String> nick = new HashMap<Player, String>();

@EventHandler
public void onChat(AsyncPlayerChatEvent e){
	Player p = e.getPlayer();
	if(nick.containsKey(p)){
		e.setCancelled(true);
		for(Player pls : Bukkit.getOnlinePlayers()){
			pls.sendMessage(nick.get(p)+": §7"+e.getMessage());
		}
	}
}

//Dans la commande:
// Pour set le nick: nick.put(Player, args[1]);