获取公网ip

1、获取公网ip的网址：http://2019.ip138.com/ic.asp

2、利用该网址获取公网ip:

   /**
     * 获取外网的IP(必须放到子线程里处理)
     */
    public static String getNetIp() {
        String ip;
        InputStream inStream ;
        try {
            URL infoUrl = new URL("http://2019.ip138.com/ic.asp");
            URLConnection connection = infoUrl.openConnection();
            HttpURLConnection httpConnection = (HttpURLConnection) connection;
            int responseCode = httpConnection.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                inStream = httpConnection.getInputStream();
                BufferedReader reader = new BufferedReader(new InputStreamReader(inStream, "gb2312"));
                StringBuilder builder = new StringBuilder();
                String line = null;
                while ((line = reader.readLine()) != null) {
                    builder.append(line);
                }
                inStream.close();
                int start = builder.indexOf("[");
                int end = builder.indexOf("]");
                ip = builder.substring(start + 1, end);
                return ip;
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }