You don't need to use the system's path separator; in fact, that will mess up Windows paths (because it will give you a '\'). With Java, paths always use a forward slash '/' and then will be translated under the hood.
It looks like your file path is wrong because you've got your resources folder in the wrong place. It should be like this:
Im assuming SteelDesigner's package is com.structures.gui - if it is, then indeed your directory hierarchy is wrong. Also your source hierarchy is strange. Typically you'd do something like this:
For example, from my LD17 entry I had:
My website is otcsw.com so that makes sense for me. Obviously you can do whatever you want, but your hierarchy is atypical.
So yeah. Move your resources folder to the location I mentioned above, then access it by:
new File(System.getProperty("user.dir") + "/resources/UBProperties.csv")
And that should do the trick.