java - Data structure that stores strings and ignores letter case -

i know hashset<string> data structure can store unique strings , if string present o(1) complexity, because uses hash code. can same complexity achieved, if want ignore letter case? next use case should work:

set<string> set = new ignorelettercaseset(); set.add("new york"); set.contains("new york") == true; set.contains("new york") == true;  set.each(it -> print it) ---> prints "new york" 

is possible implement such data structure?

just use hashmap original string value , lower case 1 key

map<string, string> map = new hashmap<>(); map.add("new york".tolowercase() ,"new york"); map.containskey("new york".tolowercase()) == true; map.containskey("new york".tolowercase()) == true;  map.values().each(it -> print it) ---> prints "new york"