public ArrayList<String> traerUsuario(Usuario u){
    conn = Conector.conectorBd();  
  
     int pa =u.getPassword();
    
     int ru =u.getRut();
        
    String sql = "SELECT u.nombre, u.coded, u.codtipousuario, e.nombre as edificio  \n" +
"from usuario u inner join edificio e\n" +
"ON(u.coded=e.cod_ed) where rut="+ru+" and password="+pa+"";           
        try {
            pst = conn.prepareStatement(sql);
            
            ArrayList<String> ls = new ArrayList<>();
            
            rs = pst.executeQuery();
            while(rs.next()){
                ls.add(rs.getString("nombre"));
                ls.add(String.valueOf(rs.getInt("coded")));
                ls.add(String.valueOf(rs.getInt("codtipousuario")));
                ls.add(rs.getString("edificio"));
            }
            return ls;
            
        } catch (Exception e) {
            return null;
        }
    
    }