combinations

public class test {
    public static void main(String[] args) {
        HashSet<String> stuff =combinations("Daniel",6,6,new HashSet<String>());
        System.out.println(stuff);
        System.out.println("length: " +stuff.size());
    }
    public static HashSet<String> combinations(String s, int k,int count, HashSet<String> set){
        s=s.toLowerCase();
        if(s.length() > k){
            Set<Character> letters = new HashSet<>();
            for (int i = 0; i < s.length(); i++) {
                if (letters.contains(s.charAt(i))) {
                    s = s.substring(0, i) + s.substring(i + 1);
                    i--;
                    System.out.println(s);
                } else {
                    letters.add(s.charAt(i));
                }
            }
            for(int i = 0; i <s.length();i++){
                String temp = s;
                set.addAll(combinations(temp.substring(0,i) + temp.substring(i+1),k,count,set));
            }
            return set;
        }
        else if(count > 1){
            for(int i = 0; i < s.length();i++){
                set.addAll(combinations(s.charAt(i) + s.substring(0,i) + s.substring(i+1),k,count-1,set));
            }
            return set;

        }
        else{
            set.add(s);
            return set;
        }
    }
}