private static final Predicate<@Nullable String> NOT_LENGTH_3 =
      input -> input == null || input.length() != 3;
  private static final Predicate<@Nullable Integer> EVEN = input -> input == null || input % 2 == 0;
  static final Predicate<Entry<String, Integer>> CORRECT_LENGTH =
      input -> input.getKey().length() == input.getValue();

  abstract Map<String, Integer> createUnfiltered();

  static <V extends @Nullable Object, X extends Throwable> ListenableFuture<V> create(
      ListenableFuture<? extends V> input,
      Class<X> exceptionType,
      Function<? super X, ? extends V> fallback,
      Executor executor) {
    CatchingFuture<V, X> future = new CatchingFuture<>(input, exceptionType, fallback);
    input.addListener(future, rejectionPropagatingExecutor(executor, future));
    return future;
  }

     * requires some work.
     */

    return Collector.of(
        ImmutableTableCollectorState<R, C, V>::new,
        (state, input) ->
            state.put(
                rowFunction.apply(input),
                columnFunction.apply(input),
                valueFunction.apply(input),
                mergeFunction),
        (s1, s2) -> s1.combine(s2, mergeFunction),
        state -> state.toTable());
  }

  static <

          A result(Collector<T, A, R> collector, Iterable<T> inputs) {
        A accum = collector.supplier().get();
        for (T input : inputs) {
          collector.accumulator().accept(accum, input);
        }
        return accum;
      }
    },
    /** Get one accumulator for each element and merge the accumulators left-to-right. */
    MERGE_LEFT_ASSOCIATIVE {
      @Override

  static <I extends @Nullable Object, O extends @Nullable Object> ListenableFuture<O> create(
      ListenableFuture<I> input,
      AsyncFunction<? super I, ? extends O> function,
      Executor executor) {
    checkNotNull(executor);
    AsyncTransformFuture<I, O> output = new AsyncTransformFuture<>(input, function);
    input.addListener(output, rejectionPropagatingExecutor(executor, output));
    return output;
  }

  }

  static void testSort(int[] input, int[] expected) {
    input = Arrays.copyOf(input, input.length);
    UnsignedInts.sort(input);
    assertThat(input).isEqualTo(expected);
  }

  static void testSort(int[] input, int from, int to, int[] expected) {
    input = Arrays.copyOf(input, input.length);
    UnsignedInts.sort(input, from, to);
    assertThat(input).isEqualTo(expected);
  }

  }

  static void testSort(long[] input, long[] expected) {
    input = Arrays.copyOf(input, input.length);
    UnsignedLongs.sort(input);
    assertThat(input).isEqualTo(expected);
  }

  static void testSort(long[] input, int from, int to, long[] expected) {
    input = Arrays.copyOf(input, input.length);
    UnsignedLongs.sort(input, from, to);
    assertThat(input).isEqualTo(expected);
  }

  }

  static void testSort(byte[] input, byte[] expected) {
    input = Arrays.copyOf(input, input.length);
    UnsignedBytes.sort(input);
    assertThat(input).isEqualTo(expected);
  }

  static void testSort(byte[] input, int from, int to, byte[] expected) {
    input = Arrays.copyOf(input, input.length);
    UnsignedBytes.sort(input, from, to);
    assertThat(input).isEqualTo(expected);
  }

  private static void testReverse(short[] input, short[] expectedOutput) {
    input = Arrays.copyOf(input, input.length);
    Shorts.reverse(input);
    assertThat(input).isEqualTo(expectedOutput);
  }

  private static void testReverse(
      short[] input, int fromIndex, int toIndex, short[] expectedOutput) {
    input = Arrays.copyOf(input, input.length);
    Shorts.reverse(input, fromIndex, toIndex);

      @Override
      public Object apply(Object input) {
        output.cancel(false);
        throw new MyError();
      }
    }
    Transformer transformer = new Transformer();
    SettableFuture<Object> input = SettableFuture.create();

    ListenableFuture<Object> output = transform(input, transformer, directExecutor());
    transformer.output = output;

    input.set("foo");
    assertTrue(output.isCancelled());