return new Object();
          }
        };
    WeakReference<Object> ref = doNextAndGetWeakReference(itr);
    GcFinalization.awaitClear(ref);
  }

  @GwtIncompatible // weak references
  private WeakReference<Object> doNextAndGetWeakReference(Iterator<Object> itr) {
    return new WeakReference<>(itr.next());
  }

  public void testReentrantHasNext() {
    Iterator<Integer> iter =

  public void testWeakImplementations() {
    for (Striped<?> striped : weakImplementations()) {
      WeakReference<Object> weakRef = getWeakReferenceToStripe(striped);
      GcFinalization.awaitClear(weakRef);
    }
  }

  private WeakReference<Object> getWeakReferenceToStripe(Striped<?> striped) {
    return new WeakReference<>(striped.get(new Object()));
  }

  public void testWeakReadWrite() {

  public void testWeakImplementations() {
    for (Striped<?> striped : weakImplementations()) {
      WeakReference<Object> weakRef = getWeakReferenceToStripe(striped);
      GcFinalization.awaitClear(weakRef);
    }
  }

  private WeakReference<Object> getWeakReferenceToStripe(Striped<?> striped) {
    return new WeakReference<>(striped.get(new Object()));
  }

  public void testWeakReadWrite() {

  }

  private static final Map<Class<? extends Enum<?>>, Map<String, WeakReference<? extends Enum<?>>>>
      enumConstantCache = new WeakHashMap<>();

  private static <T extends Enum<T>> Map<String, WeakReference<? extends Enum<?>>> populateCache(
      Class<T> enumClass) {
    Map<String, WeakReference<? extends Enum<?>>> result = new HashMap<>();
    for (T enumInstance : EnumSet.allOf(enumClass)) {

import java.lang.ref.WeakReference;
import java.util.ConcurrentModificationException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.jspecify.annotations.Nullable;

/**
 * A builder of {@link ConcurrentMap} instances that can have keys or values automatically wrapped
 * in {@linkplain WeakReference weak} references.
 *
 * <p>Usage example:

import java.lang.ref.WeakReference;
import java.util.ConcurrentModificationException;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import org.jspecify.annotations.Nullable;

/**
 * A builder of {@link ConcurrentMap} instances that can have keys or values automatically wrapped
 * in {@linkplain WeakReference weak} references.
 *
 * <p>Usage example:

    WeakReference<? extends Enum<?>> ref = Enums.getEnumConstants(enumClass).get(value);
    /*
     * We use `fromNullable` instead of `of` because `WeakReference.get()` has a nullable return
     * type.
     *
     * In practice, we are very unlikely to see `null`: The `WeakReference` to the enum constant

    AtomicReference<Object> sepStopwatchA =
        new AtomicReference<Object>(sepStopwatchC.getMethod("createUnstarted").invoke(null));
    AtomicReference<WeakReference<?>> sepStopwatchRef =
        new AtomicReference<WeakReference<?>>(
            (WeakReference<?>) sepFwrCons.newInstance(sepStopwatchA.get(), sepFrqA.get()));
    assertThat(sepStopwatchA.get()).isNotNull();

    MyInt canonical = new MyInt(5);
    MyInt not = new MyInt(5);

    Interner<MyInt> pool = Interners.newWeakInterner();
    assertThat(pool.intern(canonical)).isSameInstanceAs(canonical);

    WeakReference<MyInt> signal = new WeakReference<>(canonical);
    canonical = null; // Hint to the JIT that canonical is unreachable

    GcFinalization.awaitClear(signal);
    assertThat(pool.intern(not)).isSameInstanceAs(not);
  }

  public void testGetIfPresent_doesNotPreventClassUnloading() throws Exception {
    WeakReference<?> shadowLoaderReference = doTestClassUnloading();
    GcFinalization.awaitClear(shadowLoaderReference);
  }

  // Create a second ClassLoader and use it to get a second version of the TestEnum class.
  // Run Enums.getIfPresent on that other TestEnum and then return a WeakReference containing the