Spigot Coding Episode 5

import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.command.Command;
import org.bukkit.command.CommandSender;
import org.bukkit.entity.Player;
import org.bukkit.event.EventHandler;
import org.bukkit.event.Listener;
import org.bukkit.event.player.AsyncPlayerChatEvent;
import org.bukkit.plugin.java.JavaPlugin;

public class Core extends JavaPlugin implements Listener {

    @Override
    public void onEnable() {
        getLogger().info("has been enabled!");
        Bukkit.getServer().getPluginManager().registerEvents(this, this);
    }

    @Override
    public void onDisable() {
        getLogger().info("has been disabled!");
    }

    @EventHandler
    public void onChat(AsyncPlayerChatEvent event) {
        if (this.getConfig().getString(event.getPlayer().getName()) != null) {
            event.getPlayer().setDisplayName(this.getConfig().getString(event.getPlayer().getName()) + ChatColor.RESET);
        }
    }

    public boolean onCommand(CommandSender sender, Command cmd, String commandLabel, String[] args) {
        if (!(sender instanceof Player)) {
            sender.sendMessage("§4Console cannot have a nickname!");
        }

        Player player = (Player) sender;

        if (cmd.getName().equalsIgnoreCase("nick")) {
            if (player.hasPermission("nick.nick") || (player.isOp())) {
                if (args.length == 0) {
                    player.sendMessage("§4You did not give a §enickname§4!");
                    return true;
                }


                String nickname = "";
                for (String arg : args) {
                    nickname += arg + " ";
                }

                nickname = nickname.substring(0, nickname.length() - 1);
                nickname = nickname.replaceAll("&", "§");

                player.sendMessage("§bYou have changed your nickname from §3" + player.getName() + "§b to §e" + nickname + "§b!");
                this.getConfig().set(player.getName(), nickname);
                this.saveConfig();
            }
        }
        return false;
    }