MySQL-Manager - SPIGOT

import org.bukkit.configuration.file.YamlConfiguration;

import java.io.File;
import java.sql.*;

public class DatabaseManager {
    private String ip;
    private String dbName;
    private String usrName;
    private String password;
    private int port = 3306;
    private Connection connection;
    private boolean failedMySQL = false;

    private static DatabaseManager instance = null;

    public static DatabaseManager get() {
        return instance == null ? instance = new DatabaseManager() : instance;
    }

    public void setup(){
        File file = new File(Main.get().getDataFolder(), "MySQL.yml");
        boolean createFile = !file.exists();

        if (createFile) {
            //TODO ne neue MySQL.yml file erstllen
            failedMySQL = true;
        }else{
            YamlConfiguration mysqlFile = YamlConfiguration.loadConfiguration(file);
            ip = mysqlFile.getString( "MySQL.IP", "Unknown");
            dbName = mysqlFile.getString("MySQL.DB-Name", "Unknown");
            usrName = mysqlFile.getString("MySQL.Username", "Unknown");
            password = mysqlFile.getString("MySQL.Password", "Unknown");
            port = mysqlFile.getInt("MySQL.Port", 3306);

            connectMySQLServer();
        }

        //TODO exec statement: CREATE TABLE IF NOT EXISTS [...]
    }

    public void shutdown(){
        try {
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    private void connectMySQLServer() {
        try {
            connection = DriverManager.getConnection("jdbc:mysql://" + ip + ":" + port + "/" + dbName + "?verifyServerCertificate=false&useSSL=false&autoReconnect=true", usrName, password);
        } catch (Exception exc) {
            System.out.println("\n \n \nMySQL-Error\nCould not connect to MySQL-Server!\nCheck your MySQL.yml \n \n");
            failedMySQL = true;
        }
    }

    public void executeStatement(String sql, Object... parameters) {
        executeStatement(sql, false, parameters);
    }

    public ResultSet executeResultStatement(String sql, Object... parameters) {
        return executeStatement(sql, true, parameters);
    }

    private ResultSet executeStatement(String sql, boolean result, Object... parameters) {
        try {
            PreparedStatement statement = connection.prepareStatement(sql);

            for (int i = 0; i < parameters.length; i++) {
                Object obj = parameters[i];
                if(obj instanceof Integer)
                    statement.setInt(i + 1, (Integer) obj);
                else if(obj instanceof String)
                    statement.setString(i+1, (String) obj);
                else if(obj instanceof Long)
                    statement.setLong(i+1, (Long) obj);
                else
                    statement.setObject(i+1, obj);
            }

            if(result){
                ResultSet resultSet = statement.executeQuery();
                return resultSet;
            }else{
                statement.execute();
                statement.close();
            }
            return null;
        } catch (SQLException e) {
            System.out.println("SQL -> "+sql);
            e.printStackTrace();
            return null;
        }
    }

    public boolean isConnectionValid(int timeout){
        try {
            return connection.isValid(timeout);
        } catch (SQLException e) {
            e.printStackTrace();
            return false;
        }
    }

    public boolean isFailedMySQL() {
        return failedMySQL;
    }
}