private static void appendFromStart(final StringBuilder buffer, final String original, final int groupSize) {
    int pointer = 0;
    while (pointer + groupSize < original.length()) {
      buffer.append(original, pointer, pointer + groupSize);
      buffer.append('_');
      pointer += groupSize;
    }

    if (pointer < original.length()) {
      buffer.append(original.substring(pointer));
    }
  }
private static void appendFromStart(final StringBuilder buffer, final String original, final int groupSize)