// Returns the non-null array of replacements for fast lookup.
  char[][] getReplacementArray() {
    return replacementArray;
  }

  // Creates a replacement array from the given map. The returned array is a
  // linear lookup table of replacement character sequences indexed by the
  // original character value.
  @VisibleForTesting
  static char[][] createReplacementArray(Map<Character, String> map) {