Just bringing this to the top of the Google QueueTM, if you’re using the listFiles() method of the org.apache.commons.net.ftp.FTPFile class and you’re seeing that listFiles() returns null when it shouldn’t be, make sure to upgrade to the latest and greatest version of commons-net (which is 1.2.2 right now). Using version 1.0.0 was causing NPE’s all over the place. I think this bug on issues.apache.org discusses the issue, but it’s more specific than what I was seeing.
I have commons-net-1.2.2.jar version jar file, i am getting listFile()length always 0(zero). what was the problem.