code: @NonNull
    public Caffeine<K, V> refreshAfterWrite(@NonNull Duration duration) {
      return refreshAfterWrite(duration.toNanos(), TimeUnit.NANOSECONDS);
    }
docs: Specifies that active entries are eligible for automatic refresh once a fixed duration has
  elapsed after the entry's creation, or the most recent replacement of its value. The semantics
  of refreshes are specified in {@link LoadingCache#refresh}, and are performed by calling {@link
  CacheLoader#reload}.
  <p>
  Automatic refreshes are performed when the first stale request for an entry occurs. The request
  triggering refresh will make an asynchronous call to {@link CacheLoader#reload} and immediately
  return the old value.
  <p>
  <b>Note:</b> <i>all exceptions thrown during refresh will be logged and then swallowed</i>.
  
  @param duration the length of time after an entry is created that it should be considered
  stale, and thus eligible for refresh
  @return this {@code Caffeine} instance (for chaining)
  @throws IllegalArgumentException if {@code duration} is negative
  @throws IllegalStateException if the refresh interval was already set
  @throws ArithmeticException for durations greater than +/- approximately 292 years