static File createSnapshotFile(String name,File directory,long index,long timestamp){
  return new File(directory,String.format("%s-%d-%s.snapshot",Assert.notNull(name,"name"),index,TIMESTAMP_FORMAT.format(new Date(timestamp))));
}

static File createSnapshotFile ( String name , File directory , long index , long timestamp ) { return new File ( directory , String . format ( "%s-%d-%s.snapshot" , Assert . notNull ( name , "name" ) , index , TIMESTAMP_FORMAT . format ( new Date ( timestamp ) ) ) ) ; }
creates a snapshot file for the given directory , log name , and snapshot index .
