code: private Deque<Character> dequeFrom(CharSequence in) {
          if (in == null) {
              return null;
          }
  
          final Deque<Character> out = new ArrayDeque<>(in.length());
  
          for (int i = in.length() - 1; i >= 0; i--) {
              out.push(in.charAt(i));
          }
  
          return out;
      }
docs: Creates deque (double-side queue) of CharSequence
  
  @param in char sequence to be converted to deque
  @return characters deque