@GwtIncompatible
@ElementTypesAreNonnullByDefault
public abstract class FinalizableSoftReference<T> extends SoftReference<T>
    implements FinalizableReference {
  /**
   * Constructs a new finalizable soft reference.
   *
   * @param referent to softly reference
   * @param queue that should finalize the referent
   */
  protected FinalizableSoftReference(@CheckForNull T referent, FinalizableReferenceQueue queue) {
    super(referent, queue.queue);

      Preconditions.checkState(valueRef instanceof Reference);
      Reference<V> ref = (Reference<V>) valueRef;
      if (ref != null) {
        ref.clear();
      }
    }
  }

  /**
   * Poke into the Cache internals to simulate garbage collection of the given key. This assumes
   * that the given entry is a weak or soft reference, and throws an IllegalStateException if that
   * assumption does not hold.

 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
public final class Functions {
  private Functions() {}

  /**
   * A function equivalent to the method reference {@code Object::toString}, for users not yet using
   * Java 8. The function simply invokes {@code toString} on its argument and returns the result. It
   * throws a {@link NullPointerException} on null input.
   *

   *
   * This class isn't an arbitrary ForwardingImmutableSet because we need to
   * know that calling {@code clone()} during deserialization will return an
   * object that no one else has a reference to, allowing us to guarantee
   * immutability. Hence, we support only {@link EnumSet}.
   */
  private final transient EnumSet<E> delegate;

  private ImmutableEnumSet(EnumSet<E> delegate) {

  /** Returns a fresh {@link InternerBuilder} instance. */
  public static InternerBuilder newBuilder() {
    return new InternerBuilder();
  }

  /**
   * Returns a new thread-safe interner which retains a strong reference to each instance it has
   * interned, thus preventing these instances from being garbage-collected. If this retention is
   * acceptable, this implementation may perform better than {@link #newWeakInterner}.
   */

  /*
   * We avoid using a method reference or lambda here for now:
   *
   * - method reference: Inside Google, CacheBuilder is used from the implementation of a custom
   *   ClassLoader that is sometimes used as a system classloader. That's a problem because
   *   method-reference linking tries to look up the system classloader, and it fails because there
   *   isn't one yet.
   *

  /**
   * Returns a predicate that evaluates to {@code true} if the object reference being tested is
   * null.
   */
  @GwtCompatible(serializable = true)
  public static <T extends @Nullable Object> Predicate<T> isNull() {
    return ObjectPredicate.IS_NULL.withNarrowedType();
  }

  /**
   * Returns a predicate that evaluates to {@code true} if the object reference being tested is not
   * null.
   */

       * The future no longer needs to interrupt this task, so it no longer needs a reference to it.
       *
       * TODO(cpovirk): It might be nice for our InterruptibleTask subclasses to null out their
       *  `callable` fields automatically. That would make it less important for us to null out the
       * reference to `task` here (though it's still nice to do so in case our reference to the

  }

  private String expectedToString(Set<Entry<K, V>> entries) {
    Map<K, V> reference = new LinkedHashMap<>();
    for (Entry<K, V> entry : entries) {
      reference.put(entry.getKey(), entry.getValue());
    }
    return reference.toString();
  }

  }

  private String expectedToString(Set<Entry<K, V>> entries) {
    Map<K, V> reference = new LinkedHashMap<>();
    for (Entry<K, V> entry : entries) {
      reference.put(entry.getKey(), entry.getValue());
    }
    return reference.toString();
  }