* Futures#addCallback addCallback()}.
   *
   * <p>Memory consistency effects: Actions in a thread prior to adding a listener <a
   * href="https://docs.oracle.com/javase/specs/jls/se7/html/jls-17.html#jls-17.4.5">
   * <i>happen-before</i></a> its execution begins, perhaps in another thread.
   *
   * <p>Guava implementations of {@code ListenableFuture} promptly release references to listeners

    val relay = edit(file, pipe.source, metadata, 5)
    val future1 = executor.submit(sourceReader(relay.newSource()))
    val future2 = executor.submit(sourceReader(relay.newSource()))
    Thread.sleep(500)
    sink.writeUtf8("abcdefghij")
    Thread.sleep(500)
    sink.writeUtf8("klmnopqrst")
    sink.close()
    assertThat<ByteString>(future1.get())
      .isEqualTo("abcdefghijklmnopqrst".encodeUtf8())

 * method.
 *
 * <p>The {@code standard} methods and any collection views they return are not guaranteed to be
 * thread-safe, even when all of the methods that they depend on are thread-safe.
 *
 * @author Louis Wasserman
 */
@ElementTypesAreNonnullByDefault
public abstract class ForwardingSortedMultiset<E extends @Nullable Object>

import org.checkerframework.checker.nullness.qual.Nullable;

/**
 * An Iterator implementation which draws elements from a queue, removing them from the queue as it
 * iterates. This class is not thread safe.
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
final class ConsumingQueueIterator<T extends @Nullable Object> extends AbstractIterator<T> {
  private final Queue<T> queue;

import java.lang.ref.ReferenceQueue;
import java.lang.ref.SoftReference;
import javax.annotation.CheckForNull;

/**
 * Soft reference with a {@code finalizeReferent()} method which a background thread invokes after
 * the garbage collector reclaims the referent. This is a simpler alternative to using a {@link
 * ReferenceQueue}.
 *
 * @author Bob Lee
 * @since 2.0
 */
@J2ktIncompatible
@GwtIncompatible

    CountDownLatch doneSignal = new CountDownLatch(1);
    Thread thread =
        new Thread(
            () -> {
              try {
                cache.get(key, loader);
              } catch (UncheckedExecutionException | ExecutionException e) {
                doneSignal.countDown();
              }
            });
    thread.start();

    boolean done = doneSignal.await(1, SECONDS);

    CountDownLatch doneSignal = new CountDownLatch(1);
    Thread thread =
        new Thread(
            () -> {
              try {
                cache.get(key, loader);
              } catch (UncheckedExecutionException | ExecutionException e) {
                doneSignal.countDown();
              }
            });
    thread.start();

    boolean done = doneSignal.await(1, SECONDS);

      run = true;
    }
  }

  private static class TestCallable implements Callable<String> {
    @Override
    public String call() {
      return "foo";
    }
  }

  /** Simple same thread listening executor service that doesn't handle shutdown. */
  private static class TestListeningExecutorService extends AbstractListeningExecutorService {

    @Override
    public void execute(Runnable runnable) {

    /**
     * Ctor that creates "managed" ClassWorld. This constructor is not used in "normal" circumstances.
     */
    public ClingSupport() {
        this(new ClassWorld(CORE_CLASS_REALM_ID, Thread.currentThread().getContextClassLoader()), true);
    }

    /**
     * Ctor to be used when running in ClassWorlds Launcher.
     */
    public ClingSupport(ClassWorld classWorld) {
        this(classWorld, false);

      run = true;
    }
  }

  private static class TestCallable implements Callable<String> {
    @Override
    public String call() {
      return "foo";
    }
  }

  /** Simple same thread listening executor service that doesn't handle shutdown. */
  private static class TestListeningExecutorService extends AbstractListeningExecutorService {

    @Override
    public void execute(Runnable runnable) {