Determining age of a file in Java -


i have requirement determine how long file has been on ntfs file system.

i can read file creation time, , system time in millis, 2 not add up. off number of years. ntfs epoc 1 jan 1601 @ 0000 hrs utc, whereas java epoc 1 jan 1970. also, ntfs time given in 100's of nanoseconds.

taking account, still doesn't add up. going wrong?

public static final double secondsperjulianyear = 316880878; public static final double minutesperjulianyear = 5281347.966666667; public static final double secondsperminute = 60.0; public static final double millispersecond = 1000.0; public static final double yearsjavatimeahead = 369.0;  public static long ntfsfilecreationtime(final file file) {     filetime filecreationtime = null;     try {         path filepath = paths.get(file.touri());         if (files.exists(filepath)) {             basicfileattributes attributes = files.readattributes(filepath, basicfileattributes.class);                          filecreationtime = attributes.creationtime();         }     } catch (ioexception ex) {         ex.printstacktrace();     }     return getjavamillisfromntfstime(filecreationtime.tomillis()); }  public static long getjavamillisfromntfstime(final long ntfstime) {     double ntfsnanos = ntfstime * 100; // ntfs time unit equal 100 nanoseconds      double ntfsmillis = (ntfsnanos / 10e6); // there 10e6 nanoseconds in millisecond     double millisjavaepocahead = yearsjavatimeahead * minutesperjulianyear * secondsperminute * millispersecond;     return (long) (ntfsmillis - millisjavaepocahead); }  according windows 7, creation date is: 1/6/2016 console output of 1 of files:   system.currenttimemillis(): 1454896412295 filecreationtime(filename): -116929029460761 file age: 118383925873056

from javadoc filetime

public static filetime frommillis(long value)

returns

a filetime representing given value in milliseconds.

parameters:

value - value, in milliseconds, since epoch (1970-01-01t00:00:00z); can negative returns: filetime representing given value

note, epoch same, , time in millis.

so method should be

public static long getjavamillisfromntfstime(final long ntfstime) {      return ntfstime; }

note: when exception, can't continue , pretend didn't happen. in case nullpointerexception. suggest either don't catch ioexception or return invalid value long.min_value


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