获取公网ip

/**
 * 获取公网ip
 * @return
 */
public String getNetIp() {
    String ip = "";
    InputStream inStream = null;
    try {
        URL infoUrl = new URL("http://1212.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);
                //builder.append(line).append("\n");
            }
            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;
}