bonsoir
j'ai installé oracle 11g release 1(11.1.0.6.0) entreprise edition
j'ai utilisé sql plus pour creer un utilisateur avec tout les priviléges

create user ars identified by ben 
grant create session to ars

j'ai telecharger ojdbc6.jaret je l'ai rajouté a mon projet
et voila mon code

import java.sql.*;
public class Oracle {
  public static void main(String [] args) {
    Connection con = null;
    try {

// Load the Oracle JDBC driver
      Class.forName("oracle.jdbc.OracleDriver") ;
      System.out.println("Oracle JDBC driver loaded ok.");

      con = DriverManager.getConnection(
        "jdbc:oracle:thin:ars/ben@localhost:1521:arcl");
      System.out.println("Connected with @localhost:1521:orcl.");
      con.close();

      con = DriverManager.getConnection(
        "jdbc:oracle:thin:ars/ben@:1521:arcl");
      System.out.println("Connected with @:1521:orcl.");
      con.close();

      con = DriverManager.getConnection(
        "jdbc:oracle:thin:ars/ben@//localhost:1521/orcl");
      System.out.println("Connected with @//localhost:1521/orcl.");
      con.close();

      con = DriverManager.getConnection(
        "jdbc:oracle:thin:ars/ben@//:1521/orcl");
      System.out.println("Connected with @//:1521/orcl.");
      con.close();

      con = DriverManager.getConnection(
        "jdbc:oracle:thin:ars/ben@//localhost/orcl");
      System.out.println("Connected with @//localhost/orcl.");
      con.close();

      con = DriverManager.getConnection(
        "jdbc:oracle:thin:ars/ben@///orcl");
      System.out.println("Connected with @///orcl.");
      con.close();

      con = DriverManager.getConnection(
        "jdbc:oracle:thin:ars/ben@//localhost:1521");
      System.out.println("Connected with @//localhost:1521.");
      con.close();

    } catch (Exception e) {
      System.err.println("Exception: "+e.getMessage());
    }
  }
}

j'ai comme résultat :
Oracle JDBC driver loaded ok.
Exception: Erreur d'E/S: The Network Adapter could not establish the connection

s.v.p aidez moi

merci d'avance