code: public void flushData()
    {
      if (isClosed()) {
        if (_pendingFlushEntries.size() > 0) {
          System.out.println("PENDING_FLUSH");
        }
        return;
      }
  
      WriteStream out = _out;
      
      if (out != null) {
        try {
          out.flush();
        } catch (Exception e) {
          log.log(Level.FINER, e.toString(), e);
        }
      }
      
      // flush entries to allow for stubs to replace buffers
      completePendingFlush();
    }
docs: Flushes the buffered data to the segment.
  
  After the flush, pending entries are notified, allowing page stubs to
  replace buffered pages. Since the written data is now in the mmap, the
  buffered page can be gc'ed and replaced with a stub read.