converting to the same class while comparing (equals(Obj)) & Adding a final class

1.) Converted 'success' and 'error' to String class while comparing it with another string while applying equals(Obj).

2.) Added a final class instead of implementing a constant interface.
Thank you ! Looks good. Hopefully I will be able to do this.

I have not cloned this to my computer. So, I am not sure how will it work now.

May be first clone this repository to my computer and then compare with the origin before applying squash ?