class Replace extends EditOperation {

    @Override
    public String apply(String s) {<FILL_FUNCTION_BODY>}
  }

      if (s.length() == 0) {
        return null;
      }
      int i = random.nextInt(s.length());
      char c = randomChar(random);

      if (i == 0) {
        return "" + c + s.substring(1);
      } else if (i == s.length() - 1) {
        return s.substring(0, i) + c;
      } else {
        return s.substring(0, i) + c + s.substring(i + 1);
      }
    
<no_super_class>