code: public static Duration ofNanos(long nanos) {
          long secs = nanos / NANOS_PER_SECOND;
          int nos = (int) (nanos % NANOS_PER_SECOND);
          if (nos < 0) {
              nos += NANOS_PER_SECOND;
              secs--;
          }
          return create(secs, nos);
      }
docs: Obtains a {@code Duration} representing a number of nanoseconds.
  <p>
  The seconds and nanoseconds are extracted from the specified nanoseconds.
  
  @param nanos  the number of nanoseconds, positive or negative
  @return a {@code Duration}, not null