How to increase SFTP speed?

Question

Java

There is a utility that pumps data based on org.apache.commons.vfs2.
It is noticed that the data transfer rate through the utility is exactly 2 times less than the transfer rate displayed when copying files using the SCP command.
The question is, how to increase the transfer speed over SFTP?
org.apache.commons.vfs2.provider.ftp.FtpFileSystemConfigBuilder has a setCompression method, according to the documentation it set the value to "zlib,none", but there was no change in the transfer rate. Who can faced such trouble?