*/
  @CanIgnoreReturnValue
  @J2ktIncompatible
  @GwtIncompatible // java.time.Duration
  @ParametricNullness
  @IgnoreJRERequirement // Users will use this only if they're already using Duration.
  public static <V extends @Nullable Object> V getUninterruptibly(
      Future<V> future, Duration timeout) throws ExecutionException, TimeoutException {

     * The returned duration is calculated using {@link System#nanoTime()}
     * to ensure monotonic behavior. This duration represents the exact time
     * span between clock initialization and the current instant.
     *
     * @return the duration since clock initialization
     * @see #startInstant()
     * @see #instant()
     */
    public Duration elapsedTime() {
        long elapsedNanos = System.nanoTime() - startNanos;

      Supplier<T> delegate, Duration duration) {
    checkNotNull(delegate);
    // The alternative of `duration.compareTo(Duration.ZERO) > 0` causes J2ObjC trouble.
    checkArgument(
        !duration.isNegative() && !duration.isZero(), "duration (%s) must be > 0", duration);
    return new ExpiringMemoizingSupplier<>(delegate, toNanosSaturated(duration));
  }

  @VisibleForTesting

      Supplier<T> delegate, Duration duration) {
    checkNotNull(delegate);
    // The alternative of `duration.compareTo(Duration.ZERO) > 0` causes J2ObjC trouble.
    checkArgument(
        !duration.isNegative() && !duration.isZero(), "duration (%s) must be > 0", duration);
    return new ExpiringMemoizingSupplier<>(delegate, toNanosSaturated(duration));
  }

  @VisibleForTesting

      Runnable command, long initialDelay, long period, TimeUnit unit);

  /**
   * Duration-based overload of {@link #scheduleAtFixedRate(Runnable, long, long, TimeUnit)}.
   *
   * @since 29.0
   */
  @J2ktIncompatible
  default ListenableScheduledFuture<?> scheduleAtFixedRate(
      Runnable command, Duration initialDelay, Duration period) {
    return scheduleAtFixedRate(

internal fun checkDuration(
  name: String,
  duration: Long,
  unit: TimeUnit,
): Int {
  check(duration >= 0L) { "$name < 0" }
  val millis = unit.toMillis(duration)
  require(millis <= Integer.MAX_VALUE) { "$name too large" }
  require(millis != 0L || duration <= 0L) { "$name too small" }
  return millis.toInt()
}

internal fun checkDuration(
  name: String,
  duration: Duration,
): Int {

   * a duration in order to call a legacy API which requires a {@code long, TimeUnit} pair.
   */
  static long toNanosSaturated(Duration duration) {
    // Using a try/catch seems lazy, but the catch block will rarely get invoked (except for
    // durations longer than approximately +/- 292 years).
    try {
      return duration.toNanos();
    } catch (ArithmeticException tooBig) {

import com.google.common.annotations.J2ktIncompatible;
import java.time.Duration;

/** This class is for {@code com.google.common.base} use only! */
@J2ktIncompatible
@GwtIncompatible // java.time.Duration
final class Internal {

  /**
   * Returns the number of nanoseconds of the given duration without throwing or overflowing.
   *

  }

  static class DurationSpec {
    private final long duration;
    private final TimeUnit unit;

    private DurationSpec(long duration, TimeUnit unit) {
      this.duration = duration;
      this.unit = unit;
    }

    public static DurationSpec of(long duration, TimeUnit unit) {
      return new DurationSpec(duration, unit);
    }

    @Override
    public int hashCode() {

        void testElapsedTimeConsistency() {
            MonotonicClock clock = MonotonicClock.get();
            Instant now = clock.instant();
            Duration elapsed = clock.elapsedTime();
            Duration calculated = Duration.between(clock.startInstant(), now);

            // Allow for small timing differences (1ms) due to execution time between measurements
            assertTrue(