code: public static long download(String url, OutputStream out, boolean isCloseOut, StreamProgress streamProgress) {
  		if (StrUtil.isBlank(url)) {
  			throw new NullPointerException("[url] is null!");
  		}
  		if (null == out) {
  			throw new NullPointerException("[out] is null!");
  		}
  
  		final HttpResponse response = HttpRequest.get(url).executeAsync();
  		if (false == response.isOk()) {
  			throw new HttpException("Server response error with status code: [{}]", response.getStatus());
  		}
  		return response.writeBody(out, isCloseOut, streamProgress);
  	}
docs: 下载远程文件
  
  @param url 请求的url
  @param out 将下载内容写到输出流中 {@link OutputStream}
  @param isCloseOut 是否关闭输出流
  @param streamProgress 进度条
  @return 文件大小