code: public static <T> Collection<T> checkCollectionNotEmpty(final Collection<T> value,
                                                              final String valueName) {
          if (value == null) {
              throw new NullPointerException(valueName + " must not be null");
          }
          if (value.isEmpty()) {
              throw new IllegalArgumentException(valueName + " is empty");
          }
          return value;
      }
docs: Ensures that the {@link Collection} is not {@code null}, and contains at least one element.
  
  @param value a {@link Collection} of boxed elements.
  @param valueName the name of the argument to use if the check fails.
  
  @return the validated {@link Collection}
  
  @throws NullPointerException if the {@code value} was {@code null}
  @throws IllegalArgumentException if the {@code value} was empty