public boolean addAll(int index, Collection c) {
   validateIndex(index);
   ensureInitFastListCache();
   _cache.addAll(index, c);
   return _persistentList.addAll(index, new JdkCollectionIterable4(c));
 }
 public boolean addAll(final Collection c) {
   ensureInitFastListCache();
   _cache.addAll(c);
   return _persistentList.addAll(new JdkCollectionIterable4(c));
 }