this.nextOrNull = firstOrNull;
  }

  /**
   * Returns the element that follows {@code previous}, or returns {@code null} if no elements
   * remain. This method is invoked during each call to {@link #next()} in order to compute the
   * result of a <i>future</i> call to {@code next()}.
   */
  protected abstract @Nullable T computeNext(T previous);

  @Override
  public final boolean hasNext() {

public interface Funnel<T extends @Nullable Object> extends Serializable {

  /**
   * Sends a stream of data from the {@code from} object into the sink {@code into}. There is no
   * requirement that this data be complete enough to fully reconstitute the object later.
   *
   * @since 12.0 (in Guava 11.0, {@code PrimitiveSink} was named {@code Sink})
   */
  void funnel(@ParametricNullness T from, PrimitiveSink into);

 * #setException(Throwable)} or {@link #setFuture(ListenableFuture)} call. It can also, like any
 * other {@code Future}, be {@linkplain #cancel cancelled}.
 *
 * <p>{@code SettableFuture} is the recommended {@code ListenableFuture} implementation when your
 * task cannot be implemented with {@link ListeningExecutorService}, the various {@link Futures}

    /**
     * Gets the source from which the model was read.
     *
     * @return The source from which the model was read, never {@code null}.
     */
    @Nonnull
    ModelSource getSource();

    /**
     * Gets the file model.
     *
     * @return the file model, never {@code null}.
     */
    @Nonnull
    Model getFileModel();

    /**

 * maintained with a doubly linked list through the entries. All optional operations (put and
 * remove) are supported. Null keys and values are supported.
 *
 * <p>{@code containsKey(k)}, {@code put(k, v)} and {@code remove(k)} are all (expected and
 * amortized) constant time operations. Expected in the hashtable sense (depends on the hash

 * <td ><code>
 *  smb://host/share/foo/
 * </code></td>
 * <td ><code>
 *  ../.././.././../foo/
 * </code></td>
 * <td><code>
 *  smb://host/foo/
 * </code></td>
 * </tr>
 *
 * <tr>
 * <td ><code>
 *  smb://host/share/zig/zag
 * </code></td>
 * <td ><code>
 *  /
 * </code></td>
 * <td><code>
 *  smb://host/
 * </code></td>
 * </tr>
 *
 * <tr>
 * <td ><code>

     * the encrypted version used for key exchange.
     *
     * @return A <code>byte[]</code> containing the session key.
     */
    public byte[] getMasterKey() {
        return masterKey;
    }

    /**
     * Returns the session key.
     *
     * @return A <code>byte[]</code> containing the session key.
     */
    public byte[] getSessionKey() {
        return sessionKey;

   * following constraints. This is the callers responsibility and is not enforced here.
   *
   * <ul>
   *   <li>Both {@code xStats} and {@code yStats} must have the same {@code count}.
   *   <li>If that {@code count} is 1, {@code sumOfProductsOfDeltas} must be exactly 0.0.
   *   <li>If that {@code count} is more than 1, {@code sumOfProductsOfDeltas} must be finite.
   * </ul>
   */

 * supplied by the user of the class. For example, {@code Multiset.Entry.getElement()} returns
 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.
 *   <li>{@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
 *       String}.
 * </ul>
 *

 * supplied by the user of the class. For example, {@code Multiset.Entry.getElement()} returns
 * {@code @ParametricNullness E}, which means:
 *
 * <ul>
 *   <li>{@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
 *       String}.
 *   <li>{@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
 *       String}.
 * </ul>
 *