int index = columnIndex + 1;
  public String getColumnName (int columnIndex)  {    int index = columnIndex + 1;    StringBuffer buffer = new StringBuffer();    while (index > 0)      {	buffer.insert (0, (char) ('A' + ((index - 1) % 26)));	index = (index - 1) / 26;      }        // Return column name.    return buffer.toString();  }