}

    public User load(final User user) {
        User u = user;
        for (final AuthenticationChain chain : chains) {
            u = chain.load(u);
        }
        return u;
    }

    public void addChain(final AuthenticationChain chain) {
        chains = ArrayUtils.addAll(chains, chain);
    }

    protected StreamOf<AuthenticationChain> chains() {
        return stream(chains);
    }

            @Override
            public QueryBuilder execute(QueryContext context, Query query, float boost, FilterChain chain) {
                calledFirst.set(true);
                assertFalse(called.get());
                QueryBuilder builder = chain.execute(context, query, boost);
                assertTrue(called.get());
                return builder;
            }
        });

    protected static final String OPTIONS = "OPTIONS";

    @Override
    public void doFilter(final ServletRequest request, final ServletResponse response, final FilterChain chain)
            throws IOException, ServletException {
        final HttpServletRequest httpRequest = (HttpServletRequest) request;
        final String origin = httpRequest.getHeader("Origin");

   */
  abstract void collectOneValue(int index, @ParametricNullness InputT returnValue);

  abstract void handleAllCompleted();

  /** Adds the chain to the seen set, and returns whether all the chain was new to us. */
  private static boolean addCausalChain(Set<Throwable> seen, Throwable param) {
    // Declare a "true" local variable so that the Checker Framework will infer nullness.

    /**
     * This method simply calls <tt>negotiate( req, resp, false )</tt>
     * and then <tt>chain.doFilter</tt>. You can override and call
     * negotiate manually to achive a variety of different behavior.
     */
    @Override
    public void doFilter ( ServletRequest request, ServletResponse response, FilterChain chain ) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;

    firstException = expected;
    // Second time should also fail, with a cached causal chain.
    expected = assertThrows(PotentialDeadlockException.class, () -> lockA.lock());
    checkMessage(expected, "LockB -> LockA", "LockA -> LockB");
    // The causal chain should be cached.
    assertSame(firstException.getCause(), expected.getCause());
    // lockA should work after lockB is released.

  @CheckForNull
  ValueReference<K, V> getValueReference();

  /** Sets the value reference for this entry. */
  void setValueReference(ValueReference<K, V> valueReference);

  /** Returns the next entry in the chain. */
  @CheckForNull
  ReferenceEntry<K, V> getNext();

  /** Returns the entry's hash. */
  int getHash();

  /** Returns the key for this entry. */
  @CheckForNull
  K getKey();

  /*

   * part of the smeared hash of the element not covered by the hashtable mask, whereas the low bits
   * are the "next" pointer (pointing to the next entry in the bucket chain), which will always be
   * less than or equal to the hashtable mask.
   *
   * <pre>
   * hash  = aaaaaaaa
   * mask  = 00000fff
   * next  = 00000bbb
   * entry = aaaaabbb
   * </pre>
   *

      @Override
      boolean isCancelled() {
        return true;
      }

      @Override
      void maybeThrowOnGet(@Nullable Throwable cause) throws ExecutionException {
        // TODO(cpovirk): chain in a CancellationException created at the cancel() call?
        throw new CancellationException();
      }
    };

    boolean isDone() {
      return true;
    }

    boolean isCancelled() {

   *
   * <p>Invalid: - Collected: key/value was partially collected, but not yet cleaned up
   */
  interface InternalEntry<K, V, E extends InternalEntry<K, V, E>> {
    /** Gets the next entry in the chain. */
    E getNext();

    /** Gets the entry's hash. */
    int getHash();

    /** Gets the key for this entry. */
    K getKey();

    /** Gets the value for the entry. */
    V getValue();