使用 Channel 下載檔案

如果該檔案已存在，則會被覆蓋！

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 */ }

筆記

• 不要將捕獲塊留空！
• 如果出現錯誤，請檢查遠端檔案是否存在
• 這是一個阻塞操作，對於大檔案可能需要很長時間