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package database;

/**
 *
 * @author Skoretskiy
 */
import java.sql.*;
import oracle.jdbc.driver.*;
public class Database {
    final private static String driverName = "oracle.jdbc.driver.OracleDriver";
    private static String url;
    final private static String server = "localhost";
    final private static String port = "1521";
    final private static String sid = "XE";
    final private static String username = "lol";
    final private static String password = "lol";
    private static Connection connection;
    private static boolean isConnected = false;
    private static boolean connect() {
    try {
        url = "jdbc:oracle:thin:@" + server + ":" + port + ":" + sid;
       // url = "jdbc:oracle:thin:@" + ":/localhost"+sid;
        System.out.println(url);
        Class.forName(driverName);
        connection = DriverManager.getConnection(url, username, password);
        System.out.println("connecting: " + url);
        if(connection.equals(null))
            isConnected = false;
        else
            isConnected = true;
    } catch (ClassNotFoundException e) {
        System.out.println("ClassNotFoundException");
        isConnected = false;
    } catch (SQLException e) {
        System.out.println("SQLException\n" + e.getMessage());
        isConnected = false;
    }
    return isConnected;
    }
    public static void main(String[] args) {
        if (connect()) System.out.println("connected");
         else System.out.println("not connected");
    }
}

jdbc:oracle:thin:@localhost:1521:XE
SQLException
ORA-00604: error occurred at recursive SQL level 1
ORA-12705: Cannot access NLS data files or invalid environment specified

not connected