code: @SuppressWarnings("unchecked")
    private <T extends Indexer> T createIndexer(Class<T> indexerClass) {
      synchronized (indexerClass) {
        Indexer indexer = cache.get(indexerClass);
        if (indexer == null) {
          indexer = (Indexer) IntrospectionUtils.instantiateObject(indexerClass);
          cache.put(indexerClass, indexer);
        }
        return (T) indexer;
      }
    }
docs: Creates the Indexer of the given class.
  
  @param indexerClass
  the indexer implementation class
  @return the Indexer.