code: private void attemptDelete()
     {
        synchronized (deletable)
        {
           for (Iterator<String> it = deletable.iterator(); it.hasNext();)
           {
              String indexName = it.next();
              if (directoryManager.delete(indexName))
              {
                 it.remove();
              }
              else
              {
                 LOG.info("Unable to delete obsolete index: " + indexName);
              }
           }
        }
     }
docs: Attempts to delete all files recorded in {@link #deletable}.