code: public void index(String indexName, String indexType, List<CharSequence> jsons) {
          index(
                  jsons.stream()
                          .map(json -> new IndexRequest.IndexRequestBuilder(indexName, indexType, json.toString()).build())
                          .collect(toList())
          );
      }
docs: Index documents
  
  @param indexName target index
  @param indexType target index name
  @param jsons     documents represented as JSON