Java FTP上传创建一个空文件

When I try to upload a simple text file with the Apache Commons FTPClient and this code:

FTPClient ftp = new FTPClient();
int reply;

// connect
try {

    ftp.connect(serverAdd);
    ftp.login(username,password);
    reply = ftp.getReplyCode();

    if(FTPReply.isPositiveCompletion(reply)){
        System.out.println("Connected Success..");

        // upload file
        try {
            String fileDir = "testfile.txt";
            FileInputStream in = null;         
            in = new FileInputStream(fileDir);       
            ftp.storeFile(fileDir,in);
            System.out.println("File upload complete..");
        }catch(IOException e){
            System.out.println(e);
        }

        ftp.disconnect();
        System.out.println("Disconnected..");

    }else {
        System.out.println("Connection Failed..");
        ftp.disconnect();
    }    

} catch (SocketException ex) {
    ex.printStackTrace();
} catch (IOException ex) {
    ex.printStackTrace();
}

在 FTP 服务器的根目录中创建了一个文件，但它是空的.怎么了?上传 PDF 文件时，我已经尝试将 ftp 模式更改为 BINARY.但文件大小也是 0.

ftp.setFileType(FTP.BINARY_FILE_TYPE);