mock anonymous inner class to change outer local final variable

I have the following code snippet where the inner anonymous class will change the outer local final variable.

I want to write unite test code for this code snippet, I can write a test proxy and define my callStoredProcedure within it, although I can't figure out how I can change the outer final variable as the anonymous class does there

I am using Mockito, Any clue?

        final List<String> result = new ArrayList<String>();

        proxy.callStoredProcedure(param1, param2,
                param3, resolveSQL(param4),
                new IProxyExtractor<GenericDTO>() {

                    @Override
                    public List<GenericDTO> extract(
                            final int resultSetindex, final ResultSet rs)
                            throws SQLException {
                        while (rs.next()) {
                            result.add(rs.getString(1));
                        }

                        return Arrays
                                .asList(new GenericDTO[] { new ABCDTO() });
                    }
                }, param5, param6);