Question

1. Should I define a hashmap with something like “A” , new Character(“A”)
2. should I use something like a sorted list ? or cast it into an int?
3. simple list? (that doesnt seem too efficient )

I need a fast retrieving – when I ask if the Char exists.
adding time is almost none important.

Answer 1

As we’re talking about a Collection: It depends on the collection type. A HashSet offers the best performance for contains operations, which is O(1).

Set<Character> chars = new HashSet<Character>();
chars.add(new Character('A'));    
chars.add(new Character('B'));
chars.add(new Character('C'));

if (chars.contains('A'))
  System.out.println("Lightning fast answer: TRUE");