code: private String extractBoundary(String line) {
      // Use lastIndexOf() because IE 4.01 on Win98 has been known to send the
      // "boundary=" string multiple times.  Thanks to David Wall for this fix.
      int index = line.lastIndexOf("boundary=");
      if (index == -1) {
        return null;
      }
      String boundary = line.substring(index + 9);  // 9 for "boundary="
      if (boundary.charAt(0) == '"') {
        // The boundary is enclosed in quotes, strip them
        index = boundary.lastIndexOf('"');
        boundary = boundary.substring(1, index);
      }
  
      // The real boundary is always preceeded by an extra "--"
      boundary = "--" + boundary;
  
      return boundary;
    }
docs: Extracts and returns the boundary token from a line.
  
  @return the boundary token.