Java如何通过URL调用远程接口并读取返回信息？

        String ticket = "";//登录凭证
        String url_str = "http://www.sina.com.cn?ticket=";//获取用户认证的帐号URL
        String ticket_url = url_str + ticket;
        URL url = new URL(ticket_url);
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();
        connection.connect();

        int code = connection.getResponseCode();
        if (code == 404) {
            throw new Exception("认证无效，找不到此次认证的会话信息！");
        }
        if (code == 500) {
            throw new Exception("认证服务器发生内部错误！");
        }
        if (code != 200) {
            throw new Exception("发生其它错误，认证服务器返回 " + code);
        }
        InputStream is = connection.getInputStream();
        byte[] response = new byte[is.available()];
        is.read(response);
        is.close();
        if (response == null || response.length == 0) {
            throw new Exception("认证无效，找不到此次认证的会话信息！");
        }
        String userId = new String(response, "GBK");
        System.out.println(userId);