When a ResultSet.getXXX() method encounters a NULL in the database, it will convert it to a default value. For example, if NULL was encountered in a NUMBER field, ResultSet.getInt() will return 0. In order to determine whether or not the actual value is a NULL, wasNull() must be called. This method must be called immediately after the value is fetched from the result set. 
    
    // Fetch each row from the result set
    while (resultSet.next()) {