code: private synchronized boolean expungeStaleEntries()
      {
          if (this.size == 0) return false;
          Object r;
          boolean result = false;
          while ( (r = queue.poll()) != null)
          {
              result = true;
              SingleEntry e = (SingleEntry)r;
              this.size -= e.cleanupPkTable(this.table);
              this.nonDatedEntryCount -= e.cleanupSemiUniqueTable(this.nonDatedTable);
          }
          return result;
      }
docs: Expunge stale entries from the nonDatedTable.