public ObjectSet<Object2ObjectMap.Entry<K, V>> object2ObjectEntrySet() {
   if (entries == null) entries = ObjectSets.unmodifiable(map.object2ObjectEntrySet());
   return entries;
 }
 public ObjectSet<Object2ObjectMap.Entry<K, V>> object2ObjectEntrySet() {
   if (entries == null) entries = ObjectSets.synchronize(map.object2ObjectEntrySet(), sync);
   return entries;
 }