question: private void ensureLoaded ( ) throws IOException { if ( ! _loaded ) { if ( _backingFile != null ) { _log . debug ( "Loading buffer for index {} from {}" , _startIndex , _backingFile ) ; try ( ByteChannel in = Files . newByteChannel ( _backingFile , READ ) ) { in . read ( _buffer ) ; } } _loaded = true ; } }
target:  Loads the data from a previous flush into the buffer if it hasn't been loaded already.