public class commands implements CommandExecutor {
    @Override
    public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
        if (!(sender instanceof Player)) {
            sender.sendMessage("Only players can use that command!");
            return true;
        }
        Player player = (Player) sender;
        if (cmd.getName().equalsIgnoreCase("detector")) {
            player.getInventory().addItem(ItemManager.diamonddetect);

        }


        return true;
    }
}