@Override public long skip(long n) throws IOException {
  if (_is == null) {
    if (_s == null)     return -1;
    _is=_s.getInputStream();
  }
  return _is.skip(n);
}

@ Override public long skip ( long n ) throws IOException { if ( _is == null ) { if ( _s == null ) return - 1 ; _is = _s . getInputStream ( ) ; } return _is . skip ( n ) ; }
skips bytes in the file .
