URL url = new URL("http://www.sjtu.edu.cn/down.zip");   HttpURLConnection httpConnection = (HttpURLConnection)url.openConnection();     // 设置 User-Agent   httpConnection.setRequestProperty("User-Agent","NetFox");   // 设置断点续传的开始位置   httpConnection.setRequestProperty("RANGE","bytes=2000070");   // 获得输入流   InputStream input = httpConnection.getInputStream();