* that {@link NullPointerTester} may misbehave under Android when used on classes that rely on
   * type-use annotations.
   *
   * <p>Under j2objc, the necessary APIs exist, but some (perhaps all) return stub values, like
   * empty arrays. Presumably {@link NullPointerTester} could likewise misbehave under j2objc, but I
   * don't know that anyone uses it there, anyway.
   */
  private enum NullnessAnnotationReader {

import com.google.common.util.concurrent.Service.State;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import com.google.j2objc.annotations.J2ObjCIncompatible;
import com.google.j2objc.annotations.WeakOuter;
import java.lang.ref.WeakReference;
import java.time.Duration;
import java.util.ArrayList;
import java.util.EnumSet;
import java.util.IdentityHashMap;

import com.google.common.util.concurrent.Service.State;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.concurrent.GuardedBy;
import com.google.j2objc.annotations.J2ObjCIncompatible;
import com.google.j2objc.annotations.WeakOuter;
import java.lang.ref.WeakReference;
import java.time.Duration;
import java.util.ArrayList;
import java.util.EnumSet;
import java.util.IdentityHashMap;

   * that {@link NullPointerTester} may misbehave under Android when used on classes that rely on
   * type-use annotations.
   *
   * <p>Under j2objc, the necessary APIs exist, but some (perhaps all) return stub values, like
   * empty arrays. Presumably {@link NullPointerTester} could likewise misbehave under j2objc, but I
   * don't know that anyone uses it there, anyway.
   */
  private enum NullnessAnnotationReader {

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.j2objc.annotations.Weak;
import com.google.j2objc.annotations.WeakOuter;
import java.util.AbstractQueue;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;

import com.google.common.annotations.J2ktIncompatible;
import com.google.common.annotations.VisibleForTesting;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.j2objc.annotations.WeakOuter;
import java.util.Arrays;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
import java.util.Spliterator;
import java.util.Spliterators;

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.DoNotCall;
import com.google.errorprone.annotations.DoNotMock;
import com.google.j2objc.annotations.Weak;
import com.google.j2objc.annotations.WeakOuter;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.util.Collection;
import java.util.Comparator;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.errorprone.annotations.ForOverride;
import com.google.errorprone.annotations.concurrent.LazyInit;
import com.google.j2objc.annotations.RetainedLocalRef;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import org.jspecify.annotations.Nullable;

import static java.util.concurrent.TimeUnit.SECONDS;

import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.errorprone.annotations.DoNotMock;
import com.google.j2objc.annotations.J2ObjCIncompatible;
import java.lang.ref.WeakReference;
import java.util.Locale;
import java.util.concurrent.CancellationException;
import java.util.concurrent.CountDownLatch;

  public static <T extends @Nullable Object> Supplier<T> memoizeWithExpiration(
      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));
  }