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.
![sonar_finalclass](https://cloud.githubusercontent.com/assets/10042258/5326272/60479444-7d35-11e4-8b21-ccda069932e0.JPG)

I have done it according to this rule mentioned in sonar. Is it correct ?