If you are a Java programmer, you may already have been asked this simple, stupide question: “how to find the free disk space left on my system?”. The problem is that the answer is system dependent. Actually, it is the implementation that is system dependent.
And until very recently, there was no unique solution to answer this question, although the need has been logged in Sun’s Bug Database since June 1997. Now it is possible to get the free disk space in Java 6 with a method in the class File, which returns the number of unallocated bytes in the partition named by the abstract path name. But you might be interested in the usable disk space (the one that is writable). It is even possible to get the total disk space of a partition with the method getTotalSpace().
But if you still use JDK 5, you’ll need to use an external library such as the Apache Commons and its FileSystem class.
My IT Weblog 
Thanks a lot for this simple yet informative post. I was planning to use this on my thesis.
you can refer to http://teknoscope.com/data/java/how-to-check-the-disk-space-in-java/ for a concrete example in getting disk space information using java.