Java tutorial
import java.util.ArrayList; import java.util.Collection; import java.util.Collections; import java.util.List; public class Main { public static void main(String args[]) { List<Character> list = new ArrayList<Character>(); list.add('X'); System.out.println("Element added to list: " + list.get(0)); Collection<Character> immutableCol = Collections.unmodifiableCollection(list); immutableCol.add('Y'); } }