class UnderReplicatedBlocks implements Iterable<Block> {

  BlockIterator iterator(final int level) {
    try {
      return (BlockIterator) new HopsTransactionalRequestHandler(
          HDFSOperationType.UNDER_REPLICATED_BLKS_ITERATOR) {
        @Override
        public void acquireLock(TransactionLocks locks) throws IOException {
        }

        @Override
        public Object performTask() throws StorageException, IOException {
          return new BlockIterator(fillPriorityQueues(level), level);
        }
      }.handle();
    } catch (IOException ex) {
      BlockManager.LOG
          .error("Error while filling the priorityQueues from db", ex);
      return null;
    }
  }

    UnderReplicatedBlocks();

}