Thanks Henry, Piet,Jayesh
I updated the code to test for equality as well
Highlighted the modified part in bold, Now it seems fine and works for TreeSet, here is the output
[Canada, USA, Belgium, Afgahnistan, India, Denmark, Russia, Hungary, USA, USA, Canada, Canada, USA, usa]
[usa, USA, USA, USA, USA, Canada, Canada, Canada, Afgahnistan, Belgium, Denmark, Hungary, India, Russia]
En nu de treeset:
[usa, USA, Canada, Afgahnistan, Belgium, Denmark, Hungary, India, Russia]
treeset contains USA