code: public static <T> T checkNotEmpty(T reference,
                                         String errorMessageTemplate,
                                         Object... errorMessageArgs) {
          checkNotNull(reference, errorMessageTemplate, errorMessageArgs);
          checkArgument(not(Decisions.isEmpty()).apply(reference), errorMessageTemplate, errorMessageArgs);
          return reference;
      }
docs: Performs emptiness and nullness check. Supports the following types:
  String, CharSequence, Optional, Iterator, Iterable, Collection, Map, Object[], primitive[]