code: public String searchScroll(String scroll,String scrollId ) throws ElasticSearchException{
  		if(!this.client.isV1()) {
  			StringBuilder entity = new StringBuilder();
  			entity.append("{\"scroll\" : \"").append(scroll).append("\",\"scroll_id\" : \"").append(scrollId).append("\"}");
  			String result = this.client.executeHttp("_search/scroll",entity.toString(),ClientUtil.HTTP_GET);
  			return result;
  		}
  		else {
  			StringBuilder path = new StringBuilder();
  			path.append("_search/scroll?scroll=").append( scroll ).append( "&scroll_id=" ).append( scrollId);
  			String result = this.client.executeHttp(path.toString(), ClientUtil.HTTP_GET);
  			return result;
  		}
  //		StringBuilder entity = new StringBuilder();
  //		entity.append("{\"scroll\" : \"").append(scroll).append("\",\"scroll_id\" : \"").append(scrollId).append("\"}");
  //		String result = this.client.executeHttp("_search/scroll",entity.toString(),ClientUtil.HTTP_GET);
  //		return result;
  	}
docs: scroll search
  https://www.elastic.co/guide/en/elasticsearch/reference/6.2/search-request-scroll.html
  @param scroll
  @param scrollId
  
  @return
  @throws ElasticSearchException