/** {@inheritDoc} */
 @Override
 public boolean retainAll(Collection<?> collection) {
   boolean modified = false;
   TCharIterator iter = iterator();
   while (iter.hasNext()) {
     if (!collection.contains(Character.valueOf(iter.next()))) {
       iter.remove();
       modified = true;
     }
   }
   return modified;
 }
 /** {@inheritDoc} */
 @SuppressWarnings({"SuspiciousMethodCalls"})
 public boolean retainAll(Collection<?> collection) {
   boolean modified = false;
   TCharIterator iter = iterator();
   while (iter.hasNext()) {
     if (!collection.contains(Character.valueOf(iter.next()))) {
       iter.remove();
       modified = true;
     }
   }
   return modified;
 }