code: public XMLString substring(int beginIndex)
    {
  
      int len = m_length - beginIndex;
  
      if (len <= 0)
        return XString.EMPTYSTRING;
      else
      {
        int start = m_start + beginIndex;
  
        return new XStringForFSB(fsb(), start, len);
      }
    }
docs: Returns a new string that is a substring of this string. The
  substring begins with the character at the specified index and
  extends to the end of this string. <p>
  Examples:
  <blockquote><pre>
  "unhappy".substring(2) returns "happy"
  "Harbison".substring(3) returns "bison"
  "emptiness".substring(9) returns "" (an empty string)
  </pre></blockquote>
  
  @param      beginIndex   the beginning index, inclusive.
  @return     the specified substring.
  @exception  IndexOutOfBoundsException  if
  <code>beginIndex</code> is negative or larger than the
  length of this <code>String</code> object.