code: public static void notEmpty(Collection<?> collection, Supplier<String> message) {
      if (isEmpty(collection)) {
        throw new IllegalArgumentException(message.get());
      }
    }
docs: Asserts that the {@link Collection} is not empty.
  
  The assertion holds if and only if the {@link Collection} is not {@literal null} and contains at least 1 element.
  
  @param collection {@link Collection} to evaluate.
  @param message {@link Supplier} containing the message using in the {@link IllegalArgumentException} thrown
  if the assertion fails.
  @throws java.lang.IllegalArgumentException if the {@link Collection} is {@literal null} or empty.
  @see java.util.Collection#isEmpty()