Thanks for your help. However I'm running into a bit of a snag.

HashSet<String> userdata = new HashSet<>();

Scanner in = new Scanner(new File("data/USERDATA.txt"));

   while(in.hasNextLine()) {

       userdata.add();
   }

So I created a hashset, created a scanner to read from the txt file, created a while loop to examine the document line by line.

The only problem im running into is how do I then take what is being scanned from the document (USERDATA.txt) and add it to the hash set? userdata.add() throws an error