Hi, 1) I don't understand why cat1 in line 19 can't be resolved to a variable (the message I get from my IDE). 2) Is there another way to remove a specific cat from the set, without using a field of name? Why can't I just use the object reference? 3) I also tried in line 20: iterator.remove(cat1) - but doesn't work either.. Anyone, who can explain and help? Thank you! :)