Cannot call sendRedirect() after the response has been committed Error

Question

I'm trying to select some rows in datatable, put it in txt file to be downloaded and redirect to a jsp page, but it is not redirecting. it give me an exception

private void generateFicheiro(HttpServletRequest request, HttpServletResponse response) throws SQLException, IOException {
String outputText = "";
for(String name :  request.getParameterValues("selectedItems")) {
Conta conta = contaService.getContaByName(name);
outputText = outputText + conta.getNome() + "|" + conta.getEmail() + "|" + conta.getIdEstrutura() + "\\n";
//System.out.println(conta.getNome());
}

        response.setContentType("text/plain");
        response.setHeader("Content-Disposition", "attachment; filename = example.txt");
        try {
            //InputStream in = request.getServletContext().getResourceAsStream("/WEB-INF/example.txt");
            OutputStream outputStream = response.getOutputStream();
            //String outputResult = "This is Test";
            outputStream.write(outputText.getBytes());
            
            outputStream.flush();
            outputStream.close();
            
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        response.sendRedirect("list-ficheiro");
        return;
    }