JDBC Singleton final Connection variable with file parsing

Question

Yes, I know..I wouldn't do it the single-connection way unless I was obligated.

With that said, let's say I want to make a singleton class, say DBConnection, with an sql Connection variable, and let's say I want the class to load info from a file about the database ip, user etc inside its constructor.

How can I possibly set the Connection variable as final static, if I need to first parse data from the file before assigning value on it?

The code so far (ignore the missing synch on getConnection):

final public class DBConnection {
    transient private static Connection con;

    private DBConnection()

         [parse file, make url]
          con = DriverManager.getConnection(url);
         [...]
    }

    public static Connection getConnection(){
      if (con == null)
         new DBConnection();

    return con;

    }
}

Please also do tell if there's something awkward on the class, singleton-wise. In a sense, maybe I shouldn't have it as final after all, in case the connection closes and i have to do a new getConnection, but that would probably be a bad singleton class wouldn't it?

EDIT decided to change my aproach and make it the enum way

public enum Connect {  
    INSTANCE;
    private Connection con;
    Connect (){
      [parse file]
       con = DriverManager.getConnection(url);
     [...]
}

public Connection getCon(){
    return con;
}

However, how do I make sure noone tries

Channel.INSTANCE.getCon

before the constructor is finished?

Answer 1

If Connect.INSTANCE.getCon() is called, then the INSTANCE enum must be constructed, then its constructor must have been executed before. There's no way such code could be executed if the constructor hasn't been executed before.