code: public MetadataAdapter getMetadataAdapter() {
          if (metadataAdapter != null) return metadataAdapter;
          else {
              try {
                  return (metadataAdapter = new JavassistAdapter());
              } catch (Throwable e) {
                  if (Reflections.log != null)
                      Reflections.log.warn("could not create JavassistAdapter, using JavaReflectionAdapter", e);
                  return (metadataAdapter = new JavaReflectionAdapter());
              }
          }
      }
docs: returns the metadata adapter.
  if javassist library exists in the classpath, this method returns {@link JavassistAdapter} otherwise defaults to {@link JavaReflectionAdapter}.
  <p>the {@link JavassistAdapter} is preferred in terms of performance and class loading.