@GwtIncompatible
public class FinalizableReferenceQueueTest extends TestCase {

  private @Nullable FinalizableReferenceQueue frq;

  @Override
  protected void tearDown() throws Exception {
    frq = null;
  }


  public void testFinalizeReferentCalled() {
    final MockReference reference = new MockReference(frq = new FinalizableReferenceQueue());

    GcFinalization.awaitDone(
        new GcFinalization.FinalizationPredicate() {

    boolean finalized = finalizeCount.tryAcquire(5, SECONDS);
    assertTrue(finalized);

    Field sepFrqUserFrqF = sepFrqUserC.getField("frq");
    Closeable frq = (Closeable) sepFrqUserFrqF.get(null);
    frq.close();

    return new WeakReference<ClassLoader>(sepLoader);
  }

  private URL[] getClassPathUrls() {
    ClassLoader classLoader = getClass().getClassLoader();

 * number of well-known problems. Here is how you might use this class instead:
 *
 * <pre>{@code
 * public class MyServer implements Closeable {
 *   private static final FinalizableReferenceQueue frq = new FinalizableReferenceQueue();
 *   // You might also share this between several objects.
 *
 *   private static final Set<Reference<?>> references = Sets.newConcurrentHashSet();

      PhantomReference<Object> frqReference) {
    this.queue = queue;

    this.finalizableReferenceClassReference = new WeakReference<>(finalizableReferenceClass);

    // Keep track of the FRQ that started us so we know when to stop.
    this.frqReference = frqReference;
  }

  /** Loops continuously, pulling references off the queue and cleaning them up. */
  @SuppressWarnings("InfiniteLoopStatement")