使用 HttpURLConnection 发出 JSON POST 请求时出错

Question

如何使用 HttpURLConnection 发出 JSON POST 请求，我尝试了此代码，但出现错误：

 btn = (Button)findViewById(R.id.bbon);
        btn.setOnClickListener(new View.OnClickListener()
        {
            @RequiresApi(api = Build.VERSION_CODES.KITKAT)
            @Override
            public void onClick(View v)
            {
                try {
                    URL url = new URL ("https://reqres.in/api/users");
                    HttpURLConnection con = (HttpURLConnection)url.openConnection();
                    con.setRequestMethod("POST");
                    con.setRequestProperty("Content-Type", "application/json; utf-8");
                    con.setRequestProperty("Accept", "application/json");
                    con.setDoOutput(true);
                    String jsonInputString = "{'name': 'Table3', 'job': 'gg12344'}";
                    try(OutputStream os = con.getOutputStream()) {
                        byte[] input = jsonInputString.getBytes("utf-8");
                        os.write(input, 0, input.length);
                    }
                    try(BufferedReader br = new BufferedReader(
                            new InputStreamReader(con.getInputStream(), "utf-8"))) {
                        StringBuilder response = new StringBuilder();
                        String responseLine = null;
                        while ((responseLine = br.readLine()) != null) {
                            response.append(responseLine.trim());
                        }
                        System.out.println(response.toString());
                        Toast.makeText(getApplicationContext(),response.toString(),Toast.LENGTH_SHORT).show();
                    }
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });   

我添加了对 INTERNET 和 ACCESS_NETWORK_STATE 的权限。