Java - Conexion entre netbeans y mysql

import java.sql.*;

public class Conexion {

   private static Connection cnx = null;

   public static Connection obtener() throws SQLException, ClassNotFoundException {

      if (cnx == null) {

         try {

            cnx = DriverManager.getConnection("jdbc:mysql://localhost/java_mysql", "juan", "12345");

         } catch (SQLException ex) {

            throw new SQLException(ex);

         } catch (ClassNotFoundException ex) {

            throw new ClassCastException(ex.getMessage());

         }

      }

      return cnx;

   }

   public static void cerrar() throws SQLException {

      if (cnx != null) {

         cnx.close();

      }

   }

}