There are supposed to be two filter methods, the first one is non-recursive and second is recursive. If my input string had a space, I'd send it to the recursive method, otherwise I didn't need to use the recursive method. For a string with space, you could use the split method and send each string to the recursive method to check whether it's null. If any of the strings are null of 1 string, then you don't add the string to the anagram.