How can I convert the result of System.nanoTime to a date in Java?

Question

I want to convert the result of System.nanoTime() to a date.

public void tempBan(Player p, Player banner, int timeInSeconds){
    Long timeInNano = (long) (timeInSeconds * 10^9);
    int newTime = (int) (System.nanoTime() + timeInNano);
    // here I want to convert newTime to a date 
}

I have converted the seconds into nanoseconds by multiplying by 10^9. Now I need to convert the current system time plus the parameter which I converted into nanoseconds into a date.

Answer 1

Unfortunately, System.nanoTime() is not what you want for this.

To quote the JavaDoc:

This method can only be used to measure elapsed time and is not related to any other notion of system or wall-clock time. The value returned represents nanoseconds since some fixed but arbitrary origin time (perhaps in the future, so values may be negative). The same origin is used by all invocations of this method in an instance of a Java virtual machine; other virtual machine instances are likely to use a different origin.

You probably want System.currentTimeMillis(), in which case you can use new Date(System.currentTimeMillis() + milliseconds) to get the date for that number of milliseconds in the future.

While you could then subtract System.nanoTime(), scale the value, and add System.currentTimeMillis() to have a similar result... since you're adding System.nanoTime() anyway and therefore have the original number of seconds, you could just use System.currentTimeMillis() directly.