How to upload file with append mode？

I have many little files, i want to combine theirs into a new file on SFTP server

I have try to use RemoteFile, open file and set file open mode as 'WRITE' and 'APPEND' ,example:

```
EnumSet modeEnumSet = EnumSet.of(OpenMode.WRITE, OpenMode.APPEND);
RemoteFile rf = sftpClient.open(fileName, modeEnumSet);
try (RemoteFile.RemoteFileOutputStream os = rf.new RemoteFileOutputStream(0, 10)) {
IOUtils.write(inputStream, os);
}
```

but i found is also run as 'CREAT' mode, it's cover the file on SFTP server when write call write method

but，how to run with append mode?

Thanks！