HERE

public class main extends JavaPlugin implements Listener
{

    public void onEnable()
    {

        Bukkit.getPluginManager().registerEvents(this, this);

        getCommand("warn").setExecutor(this);

        getConfig().options().copyDefaults(true);
        saveConfig();
    }

    @SuppressWarnings("deprecation")
    @Override
    public boolean onCommand(CommandSender sender, Command command, String label, String[] args)
    {
        if ((sender instanceof Player))
        {
            Player player = (Player) sender;

            if (player.hasPermission("WHAT YOU WANT FOR PERM"))
            {
                if (args.length > 1)
                {

                    Player target = Bukkit.getPlayerExact(args[0]);

                    Integer warnings = getConfig().getInt("Warnings." + target.getUniqueId() + ".amount");

                    StringBuilder sb = new StringBuilder();
                    for (int i = 1; i < args.length; i++)
                    {
                        sb.append(args[i] + " ");
                    }
                    if(warnings <= 1 - 1)
                    {
                        getConfig().set("Warnings." + target.getUniqueId() + ".amount", getConfig().getInt("Warnings." + target.getUniqueId() + ".amount") + 1);

                        saveConfig();

                        warnings = getConfig().getInt("Warnings." + target.getUniqueId() + ".amount");

                        player.sendMessage(ChatColor.GREEN +
                                "You've warned " + target.getName() + " for `" + sb.toString().trim() + "`."
                                        + " Warning count: " + ChatColor.WHITE + "(" + ChatColor.BLUE + warnings + ChatColor.WHITE + ")");
                        target.sendMessage(ChatColor.RED +
                                "You've been warned for `" + sb.toString().trim() + "` by " + player.getName() + ".");

                    } else
                    {
                        if(warnings == 2 - 1)
                        {
                            getConfig().set("Warnings." + target.getUniqueId() + ".amount", getConfig().getInt("Warnings." + target.getUniqueId() + ".amount") + 1);

                            target.kickPlayer(ChatColor.YELLOW +
                                    "You're on your second warning. DO NOT do it again. Reason: " + sb.toString().trim() + " by " + player.getName());

                            saveConfig();

                            warnings = getConfig().getInt("Warnings." + target.getUniqueId() + ".amount");

                            player.sendMessage(ChatColor.GREEN +
                                    "You've warned " + target.getName() + " for `" + sb.toString().trim() + "`."
                                            + " Warning count: " + ChatColor.WHITE + "(" + ChatColor.BLUE + warnings + ChatColor.WHITE + ")");

                        } else if (warnings == 3 - 1)
                        {
                            getConfig().set("Warnings." + target.getUniqueId() + ".amount", getConfig().getInt("Warnings." + target.getUniqueId() + ".amount") + 1);

                            target.kickPlayer(ChatColor.RED + "You're on your third warning and are now banned. Reason: " + sb.toString().trim() + " by " + player.getName());
                            target.setBanned(true);

                            saveConfig();

                            warnings = getConfig().getInt("Warnings." + target.getUniqueId() + ".amount");

                            player.sendMessage(ChatColor.GREEN +
                                    "You've warned " + target.getName() + " for `" + sb.toString().trim() + "`."
                                            + " Warning count: " + ChatColor.WHITE + "(" + ChatColor.BLUE + warnings + ChatColor.WHITE + ")");

                        }
                    }
                    } else
                    {
                        player.sendMessage(ChatColor.GREEN + "/Warn <name> <reason>");
                    }
                } else
                {
                    player.sendMessage(ChatColor.RED + "You do not have permission to use this command.");
            }
        }
        return false;
    }

    @EventHandler
    public void onJoin(PlayerJoinEvent e)
    {
        if(!(getConfig().contains("Warnings." + e.getPlayer().getUniqueId())))
        {
            getConfig().set("Warnings." + e.getPlayer().getUniqueId() + ".amount", 0);
            System.out.println("Added to the database (config)");
            saveConfig();
        } else
        {
            System.out.println("Already added to configuration.");
        }
    }

    @EventHandler
    public void onLeave(PlayerQuitEvent e)
    {
        saveConfig();
    }
}