使用 Channel 下载文件

如果该文件已存在，则会被覆盖！

String fileName     = "file.zip";                  // name of the file
String urlToGetFrom = "http://www.mywebsite.com/"; // URL to get it from
String pathToSaveTo = "C:\\Users\\user\\";         // where to put it

//If the file already exists, it will be overwritten!
  
//Opening OutputStream to the destination file
try (ReadableByteChannel rbc = 
      Channels.newChannel(new URL(urlToGetFrom + fileName).openStream()) ) {
    try ( FileChannel channel = 
        new FileOutputStream(pathToSaveTo + fileName).getChannel(); ) {
      channel.transferFrom(rbc, 0, Long.MAX_VALUE);
    }
    catch (FileNotFoundException e) { /* Output directory not found */ }
    catch (IOException e)           { /* File IO error */ }
}
catch (MalformedURLException e)     { /* URL is malformed */ }
catch (IOException e)               { /* IO error connecting to website */ }

笔记

• 不要将捕获块留空！
• 如果出现错误，请检查远程文件是否存在
• 这是一个阻塞操作，对于大文件可能需要很长时间