public static <T> Set<T> emptySet(final Set<T> set) {
    return (set != null ? set : Collections.emptySet());
  }
Null-safe implementation for method invocations that return a Set Collection. If the returned
Set is null, then this method will return an empty Set in it's place.
<p>

@param <T> the class type of the Set's elements.
@param set the target Set to verify as not null.
@return the specified Set if not null otherwise return an empty Set.
geode-core/src/main/java/org/apache/geode/internal/util/CollectionUtils.java