Plugin Help Adding two integers together.

I am making a balance plugin that saves a players money into a config file. I have a /cash command that shows the player their balance, a /setcash command that sets the players balance and a /addcash command that adds to the players balance. The /cash and /setcash commands work perfectly. However, when i try to add to the players balance it wont work. Here is what i have for my /addcash command:

Code:

} else if (cmd.getName().equalsIgnoreCase("addcash")) {
            if (!(sender instanceof Player)) {
                sender.sendMessage(tag + ChatColor.RED + "You must be a player!");
                return true;
            } else {
                Player p = (Player) sender;
                if (args.length == 0) {
                    sender.sendMessage(tag + ChatColor.RED + " Usage: /addcash <amount>");
                    return true;
                } else {
                    String amount = args[0];
                    if (args.length == 1) {
                        String bal = getConfig().getString("Balance." + p.getName());
                        if (isInt(amount)) {
                            int num = Integer.parseInt(amount);
                            getConfig().set(bal, bal+num);
                            saveConfig();
                            p.sendMessage(ChatColor.DARK_AQUA + "You added" + ChatColor.AQUA + " $" + num + ChatColor.DARK_AQUA + " to your balance.");
                            return true;
                        }else if (isDouble(amount)) {
                            double num = Double.parseDouble(amount);
                            getConfig().set(bal, bal+num);
                            saveConfig();
                            p.sendMessage(ChatColor.DARK_AQUA + "You added" + ChatColor.AQUA + " $" + num + ChatColor.DARK_AQUA + " to your balance.");
                            return true;                       
                        }else {
                            p.sendMessage(tag + ChatColor.RED + " '" + amount + "' is not a number.");
                            return true;
                        }
                    }else {
                        p.sendMessage(tag + ChatColor.RED + " Usage: /addcash <amount>");
                        return true;
                    }
                }
            }
        }

Am i trying to add the numbers together wrong? I need help with this asap please.
Thanks

Matty

 

You're trying to add a string and an int together
bal is a String and num is an int
instead of using getConfig.getString(), use getConfig.getInt() for bal, also change bal to an int