如何等待HttpURLConnection完成?

如果我将100K文件上传到我服务的某个url,wget需要约20秒才能完成:

wget --quiet --post-file data.txt --output-document - --header "Content-Type: text/csv" http://localhost:8080/ingest

                HttpURLConnection con = (HttpURLConnection) url.openConnection();
                con.setRequestMethod("POST");
                con.setRequestProperty("Content-Type", "text/csv;charset=UTF-8");
                con.setDoOutput(true);
                OutputStream outputStream = con.getOutputStream();
                outputStream.write(str.getBytes("UTF-8"));
                outputStream.flush();
                outputStream.close();
                System.out.println("code=" + con.getResponseCode());
                BufferedReader in = new BufferedReader(
                        new InputStreamReader(con.getInputStream()));
                String inputLine;
                StringBuffer response = new StringBuffer();
                while ((inputLine = in.readLine()) != null) {
                    response.append(inputLine);
                }
                in.close();

所以我的猜测是,实际上这段代码并不是在等待提交数据,而是在后台完成的。如何强制它阻塞,直到实际数据传输完成?