code: public void exportAsFdf(FdfWriter writer) {
          for (Iterator it = fields.entrySet().iterator(); it.hasNext();) {
              Map.Entry entry = (Map.Entry)it.next();
              Item item = (Item)entry.getValue();
              String name = (String)entry.getKey();
              PdfObject v = item.getMerged(0).get(PdfName.V);
              if (v == null)
                  continue;
              String value = getField(name);
              if (lastWasString)
                  writer.setFieldAsString(name, value);
              else
                  writer.setFieldAsName(name, value);
          }
      }
docs: Export the fields as a FDF.
  
  @param writer the FDF writer