Java 8 Instant.now() with nanosecond resolution?

Question

Java 8's java.time.Instant stores in "nanosecond resolution", but using Instant.now() only provides millisecond resolution...

Instant instant = Instant.now(); System.out.println(instant); System.out.println(instant.getNano()); 

Result...

2013-12-19T18:22:39.639Z 639000000 

How can I get an Instant whose value is 'now', but with nanosecond resolution?

Answer 1

While default Java8 clock does not provide nanoseconds resolution, you can combine it with Java ability to measure time differences with nanoseconds resolution, thus creating an actual nanosecond-capable clock.

public class NanoClock extends Clock {     private final Clock clock;      private final long initialNanos;      private final Instant initialInstant;      public NanoClock()     {         this(Clock.systemUTC());     }      public NanoClock(final Clock clock)     {         this.clock = clock;         initialInstant = clock.instant();         initialNanos = getSystemNanos();     }      @Override     public ZoneId getZone()     {         return clock.getZone();     }      @Override     public Instant instant()     {         return initialInstant.plusNanos(getSystemNanos() - initialNanos);     }      @Override     public Clock withZone(final ZoneId zone)     {         return new NanoClock(clock.withZone(zone));     }      private long getSystemNanos()     {         return System.nanoTime();     } } 

Using it is straightforward: just provide extra parameter to Instant.now(), or call Clock.instant() directly:

    final Clock clock = new NanoClock();        final Instant instant = Instant.now(clock);     System.out.println(instant);     System.out.println(instant.getNano()); 

Although this solution might work even if you re-create NanoClock instances every time, it's always better to stick with a stored clock initialized early in your code, then used wherever it's needed.