@Override
  public CharSequence subSequence(int start, int end) {
    if (start == 0 && end == 1) return this;
    if (start < 0) throw new IndexOutOfBoundsException("Start index out of range:" + start);
    if (end > 1 || end < 0) throw new IndexOutOfBoundsException("End index out of range:" + end);
    if (start > end) throw new IndexOutOfBoundsException("Start index should be less or equal to end index:" + start + " - " + end);
    return "";
  }
@Override
  public CharSequence subSequence(int start, int end)