First we get the Files in the /Volumes. Then we do a loop to check if some new Files appear in /Volumes, if so, we consider it is an USB device.
We use java Thread to run to program more efficiently.
When the process runs, a quite small windows will appear on the screen. But we can press the "hide" button to undisplay the windows, so that no one knows you are copying files from USB device. So you can steal files from other people's USB device.