code: public static String stripCharsInBag(String s, String bag) {
          int i;
          String returnString = "";
  
          // Search through string's characters one by one.
          // If character is not in bag, append to returnString.
          for (i = 0; i < s.length(); i++) {
              char c = s.charAt(i);
  
              if (bag.indexOf(c) == -1) returnString += c;
          }
          return returnString;
      }
docs: Removes all characters which appear in string bag from string s.