question: private TransportNetwork checkCached ( String networkId ) { try { String filename = networkId + "_" + R5Version . version + ".dat" ; File cacheLocation = new File ( cacheDir , networkId + "_" + R5Version . version + ".dat" ) ; if ( cacheLocation . exists ( ) ) LOG . info ( "Found locally-cached TransportNetwork at {}" , cacheLocation ) ; else { LOG . info ( "No locally cached transport network at {}." , cacheLocation ) ; if ( sourceBucket != null ) { LOG . info ( "Checking for cached transport network on S3." ) ; S3Object tn ; try { tn = s3 . getObject ( sourceBucket , filename ) ; } catch ( AmazonServiceException ex ) { LOG . info ( "No cached transport network was found in S3. It will be built from scratch." ) ; return null ; } cacheDir . mkdirs ( ) ; LOG . info ( "Copying pre-built transport network from S3 to local file {}" , cacheLocation ) ; FileOutputStream fos = new FileOutputStream ( cacheLocation ) ; InputStream is = tn . getObjectContent ( ) ; try { ByteStreams . copy ( is , fos ) ; } finally { is . close ( ) ; fos . close ( ) ; } } else { LOG . info ( "Transport network was not found" ) ; return null ; } } LOG . info ( "Loading cached transport network at {}" , cacheLocation ) ; FileInputStream fis = new FileInputStream ( cacheLocation ) ; try { return TransportNetwork . read ( fis ) ; } finally { fis . close ( ) ; } } catch ( Exception e ) { LOG . error ( "Exception occurred retrieving cached transport network" , e ) ; return null ; } }
target:  If this transport network is already built and cached, fetch it quick 