assertLessThan(NEW, TERMINATED);

    assertLessThan(STARTING, RUNNING);
    assertLessThan(STARTING, STOPPING);
    assertLessThan(STARTING, FAILED);

    assertLessThan(RUNNING, STOPPING);
    assertLessThan(RUNNING, FAILED);

    assertLessThan(STOPPING, FAILED);
    assertLessThan(STOPPING, TERMINATED);
  }

  private static <T extends Comparable<? super T>> void assertLessThan(T a, T b) {

    READY,
    NOT_READY,
    DONE,
    FAILED,
  }

  @CheckForNull private T next;

  @CheckForNull
  protected abstract T computeNext();

  @CanIgnoreReturnValue
  @CheckForNull
  protected final T endOfData() {
    state = State.DONE;
    return null;
  }

  @Override
  public final boolean hasNext() {
    checkState(state != State.FAILED);
    switch (state) {
      case DONE:

    try {
      unicodeEscaper.escape("\uD800x\uDC00");
      fail("should have failed for bad Unicode input");
    } catch (IllegalArgumentException e) {
      // pass
    }
    assertEquals("<lo><hi>", charEscaper.escape("\uDC00\uD800"));
    try {
      unicodeEscaper.escape("\uDC00\uD800");
      fail("should have failed for bad Unicode input");
    } catch (IllegalArgumentException e) {
      // pass
    }

                throw exception;
              }
            });
    T wrapper = wrapperFunction.apply(proxy);
    try {
      method.invoke(wrapper, getParameterValues(method));
      fail(method + " failed to throw exception as is.");
    } catch (InvocationTargetException e) {
      if (exception != e.getCause()) {
        throw new RuntimeException(e);
      }
    } catch (IllegalAccessException e) {

                throw exception;
              }
            });
    T wrapper = wrapperFunction.apply(proxy);
    try {
      method.invoke(wrapper, getParameterValues(method));
      fail(method + " failed to throw exception as is.");
    } catch (InvocationTargetException e) {
      if (exception != e.getCause()) {
        throw new RuntimeException(e);
      }
    } catch (IllegalAccessException e) {

    Map<V, K> backwardDelegate = Maps.newHashMapWithExpectedSize(n);
    for (int i = 0; i < n; i++) {
      // requireNonNull is safe because the first `n` elements have been filled in.
      Entry<K, V> e = RegularImmutableMap.makeImmutable(requireNonNull(entryArray[i]));
      entryArray[i] = e;
      V oldValue = forwardDelegate.putIfAbsent(e.getKey(), e.getValue());
      if (oldValue != null) {

       *
       * This read is guaranteed to get us the right value because we only set this once (here).
       *
       * requireNonNull is safe because either our compareAndSet succeeded or it failed because
       * another thread did it for us.
       */
      seenExceptionsLocal = requireNonNull(seenExceptions);
    }
    return seenExceptionsLocal;
  }

    assertLessThan(NEW, TERMINATED);

    assertLessThan(STARTING, RUNNING);
    assertLessThan(STARTING, STOPPING);
    assertLessThan(STARTING, FAILED);

    assertLessThan(RUNNING, STOPPING);
    assertLessThan(RUNNING, FAILED);

    assertLessThan(STOPPING, FAILED);
    assertLessThan(STOPPING, TERMINATED);
  }

  private static <T extends Comparable<? super T>> void assertLessThan(T a, T b) {

  }

  @Override
  public final boolean hasNext() {
    checkState(state != State.FAILED);
    switch (state) {
      case DONE:
        return false;
      case READY:
        return true;
      default:
    }
    return tryToComputeNext();
  }

  private boolean tryToComputeNext() {
    state = State.FAILED; // temporary pessimism
    next = computeNext();
    if (state != State.DONE) {

                e);
      } catch (Throwable errorInLogging) { // sneaky checked exception
        // If logging fails, e.g. due to missing memory, at least try to log the
        // message and the cause for the failed logging.
        System.err.println(e.getMessage());
        System.err.println(errorInLogging.getMessage());
      } finally {
        runtime.exit(1);
      }
    }
  }