how to get the fields of all the rows of a SQL query in Java?

Good afternoon someone could help me with the following please ... I want to obtain the ID of the rows obtained by the following SQL query and save them in a variable but I do not know how to do it.

SELECT * FROM productos;

But if I know how to obtain the columns of a specific row and save them in a variable, the code I use to obtain the columns is as follows:

Connection con;
    //Obtenemos datos de tabla producto
    try {
    con = DriverManager.getConnection("jdbc:mysql://localhost:3306/susyken", "root", "");
    String sentencia = "SELECT * FROM producto WHERE Id_Producto="+codigo+";";
    Statement stmt = null; //Esto sustituirá a ps
    stmt = con.createStatement(); //Usamos create... no prepare...
    ResultSet rs = stmt.executeQuery(sentencia);
    while (rs.next()) {
        idProducto = rs.getString(1); //Si codigo es del tipo numérico en la BD debes usar getInt
        nombreProducto = rs.getString(2);
        existencia = rs.getString(3);
        precio = rs.getString(4);
    }
    } catch (SQLException ex) {
        JOptionPane.showMessageDialog(null, "Error");
    }

Could someone help me know how to do it?