question: public static void write ( Path reportingPath , double value , long ts ) throws IOException { try ( DataOutputStream dos = new DataOutputStream ( Files . newOutputStream ( reportingPath , StandardOpenOption . CREATE , StandardOpenOption . APPEND ) ) ) { dos . writeDouble ( value ) ; dos . writeLong ( ts ) ; dos . flush ( ) ; } }
target:  Simply writes single reporting entry to disk (16 bytes). Reporting entry is value (double) and timestamp (long)