code: @NullSafe
    public static <T> Enumeration<T> nullSafeEnumeration(Enumeration<T> enumeration) {
      return enumeration != null ? enumeration : Collections.emptyEnumeration();
    }
docs: Null-safe method returning the given {@link Enumeration} or an empty {@link Enumeration} if null.
  
  @param <T> Class type of the elements in the {@link Enumeration}.
  @param enumeration {@link Enumeration} to evaluate.
  @return the given {@link Enumeration} or an empty {@link Enumeration} if null.
  @see java.util.Collections#emptyEnumeration()
  @see java.util.Enumeration