docs: @VisibleForTesting
    static char[][] createReplacementArray(Map<Character, String> map) {
      checkNotNull(map); // GWT specific check (do not optimize)
      if (map.isEmpty()) {
        return EMPTY_REPLACEMENT_ARRAY;
      }
      char max = Collections.max(map.keySet());
      char[][] replacements = new char[max + 1][];
      for (char c : map.keySet()) {
        replacements[c] = map.get(c).toCharArray();
      }
      return replacements;
    }