Acessando Banco de dados

import java.io.*;
import java.sql.*;
import java.util.*;

public final class SingleDBConn {

  /**
   * dados da conexao
   */
    private String urlstring="";
    private String dbuser="";
    private String dbuserpwd="";
    private String drive="";

  /**
   * referência única
   */
  private static SingleDBConn instance = null;

  /**
   * atributos conexao 
   */
  private static Connection connection = null;

  /**
   * construtor privado
   */
  private SingleDBConn() {
     try{
         Class.forName(drive);
         connection = java.sql.DriverManager.getConnection(urlstring, dbuser, dbuserpwd);
    }catch(SQLException e){
          e.printStackTrace();
    }
  }

  /**
   * retorna conexão única
   */
  public static Connection getConnection() {
    if (instance==null) {
      instance = new SingleDBConn();
    }
    return connection;
  }

  public static void main(String arg[]){
     System.out.println(   SingleDBConn.getConnection() );

  }

}