如何显示我们已下载了多少数据

File f = new File(\"absolutepath\");
    if(f.exists()){
    f.length()
    }

URL u = new URL(\"http://www.java2s.com/binary.dat\");
    URLConnection uc = u.openConnection();
    String contentType = uc.getContentType();
    int contentLength = uc.getContentLength();
    if (contentType.startsWith(\"text/\") || contentLength == -1) {
      throw new IOException(\"This is not a binary file.\");
    }
    InputStream raw = uc.getInputStream();
    InputStream in = new BufferedInputStream(raw);
    byte[] data = new byte[contentLength];
    int bytesRead = 0;
    int offset = 0;
    while (offset < contentLength) {
      bytesRead = in.read(data, offset, data.length - offset);
      if (bytesRead == -1)
        break;
      offset += bytesRead;
    }
    in.close();