for DEV

//Code of eventHandler
public class StMenuListener implements Listener {

    private final ConfigManager configManager;

    public StMenuListener(ConfigManager configManager) {
        this.configManager = configManager;
    }

    @EventHandler

    public void onInventoryDrag(InventoryDragEvent event) {
        String stMenuTitle = configManager.getString("lang.yml", "st.st-title");
        String stMenuColor = TextColorUtil.colorize(stMenuTitle);

        if (ChatColor.stripColor(event.getView().getTitle()).equals(ChatColor.stripColor(stMenuColor))) {
            event.setCancelled(true);
        }
    }
}


//ConfigManager
public class ConfigManager {

    private static FileConfiguration getConfig(String fileName) {
        File pluginFolder = new File("plugins/EndiumMMO");
        if (!pluginFolder.exists()) {
            boolean created = pluginFolder.mkdirs();
            if (!created) {
                System.out.println("Unable to create: " + pluginFolder);
            }
        }

        File file = new File("plugins/EndiumMMO", fileName);
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                System.out.println("Failed to create " + fileName);
            }
        }
        return YamlConfiguration.loadConfiguration(file);
    }

    public static String getString(String fileName, String path) {
        FileConfiguration config = getConfig(fileName);
        return config != null ? config.getString(path) : null;
    }

    public static int getInt(String fileName, String path) {
        FileConfiguration config = getConfig(fileName);
        return config != null ? config.getInt(path) : 0;
    }

    public static boolean getBoolean(String fileName, String path) {
        FileConfiguration config = getConfig(fileName);
        return config != null && config.getBoolean(path);
    }

    public static List<String> getStringList(String fileName, String path) {
        FileConfiguration config = getConfig(fileName);
        return config != null ? config.getStringList(path) : null;
    }

    public static List<Integer> getIntegerList(String fileName, String path) {
        FileConfiguration config = getConfig(fileName);
        return config != null ? config.getIntegerList(path) : null;
    }

    public static void setValue(String fileName, String path, Object value) {
        File file = new File("plugins/EndiumMMO", fileName);
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException e) {
                System.out.println("Failed to create " + fileName);
            }
        }
        FileConfiguration config = YamlConfiguration.loadConfiguration(file);

        config.set(path, value);

        try {
            config.save(file);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void setIntListInline(String fileName, String path, List<Integer> list) {
        String inlineList = list.toString();

        setValue(fileName, path, inlineList);
    }

    public static List<Integer> getIntListInline(String fileName, String path) {
        String listString = getString(fileName, path);
        if (listString == null || listString.isEmpty()) {
            return null;
        }

        return Arrays.stream(listString.replace("[", "").replace("]", "").split(","))
                .map(String::trim)
                .map(Integer::parseInt)
                .collect(Collectors.toList());
    }
}


//TextColorUtil
public class TextColorUtil {
    public static String colorize(String text) {
        return ChatColor.translateAlternateColorCodes('&', text);
    }

    public static String removeColors(String text) {
        return ChatColor.stripColor(text);
    }
}


//GUI
public class StatisticGUI {

    public StatisticGUI(Player player, Player target) {

        ConfigManager configManager = new ConfigManager();
        String targetName = target.getName();
        int sizeMenu = ConfigManager.getInt("guis/st.yml", "st.menu-size");
        String stMenuTitle = ConfigManager.getString("lang.yml", "st.st-title").replace("{player}", targetName);
        String stMenuColor = TextColorUtil.colorize(stMenuTitle);
        Inventory inventory = Bukkit.createInventory(null, sizeMenu, stMenuColor);

        List<Integer> fillMaterialList = configManager.getIntListInline("guis/st.yml", "st.material-slots");
        String materialFill = configManager.getString("guis/st.yml", "st.material-fill");
        Material materialConfigFill = Material.valueOf(materialFill);
        ItemStack materialStack = new ItemStack(materialConfigFill, 1);

        for (int slot : fillMaterialList) {
            if (slot >= 0 && slot < inventory.getSize()) {
                inventory.setItem(slot, materialStack);
            }

            player.openInventory(inventory);
        }
    }
}