code: static void deleteAllFiles(SolrClient client) throws IOException, SolrServerException {
  
          if (null == client) {
              return;
          }
  
          client.deleteByQuery("*:*");
          client.commit();
      }
docs: Deletes all documents from the Solr client.<p>
  
  @param client The SolrClient instance object.
  
  @throws IOException in case something goes wrong
  @throws SolrServerException in case something goes wrong