I was writing a small application and when I tried to create an ImageIcon I always got an exception. The exception was caused by this line of code:
prayerLev
Old thread but since I bumped into a similar problem just now...
I'm using Eclipse and I copied a file to the "resources" folder using system commands (cp). However, eclipse threw a NullPointerException because I didn't refresh the "resources" folder. So the file was there but Eclipse didn't see it.
So in Eclipse: "Package Explorer" -> "resources" -> Mouse right click -> refresh. This fixed it for me.