o create a random order of character java with every character and no dublicate without Random class

is there any other method to create a random order of character java with every character and with out dublicate? like without importing random class

 public static String Ra(double jav){

                Random in = new Random();
                String ans = "";
                for (int j = 0; j < jav;) {
                    char x = (char) (in.nextInt(26) + 'A');
                    if(!ans.toString().contains(""+x)){
                        ans = ans +x;
                        j++;
                    }
                }
                return ans;
            }