code: public void export(Iterator<Variant> iterator) {
          // sanity check
          if (writer == null) {
              logger.error("Error exporting VCF data: exporter must be opened");
              return;
          }
  
          // main loop (from iterator)
          while (iterator.hasNext()) {
              try {
                  VariantContext variantContext = variantConverter.convert(iterator.next());
                  //System.out.println(variantContext.toString());
                  writer.add(variantContext);
              } catch (Exception e) {
                  logger.error("Error exporting VCF data: {}", e.getMessage(), e);
              }
          }
  
  //      // close everything
  //      close();
      }
docs: Export variants in VCF file format from a variant iterator.
  
  @param iterator          Variant iterator