*/
@GwtCompatible
@ElementTypesAreNonnullByDefault
abstract class AbstractIterator<T extends @Nullable Object> implements Iterator<T> {
  private State state = State.NOT_READY;

  protected AbstractIterator() {}

  private enum State {
    READY,
    NOT_READY,
    DONE,
    FAILED,
  }

  @CheckForNull private T next;

  @CheckForNull
  protected abstract T computeNext();

  @CanIgnoreReturnValue

      // should never reach here!
      throw new UnsupportedOperationException();
    }

    @Override
    public Entry<K, V> belowSamplesGreater() {
      // should never reach here!
      throw new UnsupportedOperationException();
    }

    @Override
    public Entry<K, V> aboveSamplesLesser() {
      // should never reach here!
      throw new UnsupportedOperationException();

    MapMaker maker = new MapMaker();
    try {
      maker.initialCapacity(-1);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  // TODO(cpovirk): enable when ready (apparently after a change to our GWT emulation)
  public void xtestInitialCapacity_setTwice() {
    MapMaker maker = new MapMaker().initialCapacity(16);
    try {
      // even to the same value is not allowed

          } else if (endOfInput) { // (b)
            doneEncoding = true;
          } else { // (c)
            readMoreChars();
          }
        } else if (result.isError()) {
          // Only reach here if a CharsetEncoder with non-REPLACE settings is used.
          result.throwException();
          return 0; // Not called.
        }
      }
    }
  }

  }

  public void testSimpleWithWait() {
    RateLimiter limiter = RateLimiter.create(5.0, stopwatch);
    limiter.acquire(); // R0.00
    stopwatch.sleepMillis(200); // U0.20, we are ready for the next request...
    limiter.acquire(); // R0.00, ...which is granted immediately
    limiter.acquire(); // R0.20
    assertEvents("R0.00", "U0.20", "R0.00", "R0.20");
  }

  @CheckForNull
  public abstract C previous(C value);

  /**
   * Returns a signed value indicating how many nested invocations of {@link #next} (if positive) or
   * {@link #previous} (if negative) are needed to reach {@code end} starting from {@code start}.
   * For example, if {@code end = next(next(next(start)))}, then {@code distance(start, end) == 3}
   * and {@code distance(end, start) == -3}. As well, {@code distance(a, a)} is always zero.

  /**
   * Resets variables maintaining the sum to zero. This method may be a useful alternative to
   * creating a new adder, but is only effective if there are no concurrent updates. Because this
   * method is intrinsically racy, it should only be used when it is known that no threads are
   * concurrently updating.
   */
  public void reset() {
    internalReset(0L);
  }

  /**

   * than CPUs, supposing that each thread were bound to a CPU,
   * there would exist a perfect hash function mapping threads to
   * slots that eliminates collisions. When we reach capacity, we
   * search for this mapping by randomly varying the hash codes of
   * colliding threads.  Because search is random, and collisions
   * only become known via CAS failures, convergence can be slow,

   *
   * 1. visibility of the writes to these fields to Fire.run:
   *
   * The initial write to delegateRef is made definitely visible via the semantics of
   * addListener/SES.schedule. The later racy write in cancel() is not guaranteed to be observed,
   * however that is fine since the correctness is based on the atomic state in our base class. The

    // should be reading the byte at index 10.
    // We could use a custom InputStream instead to make the read start at index 10, but since this
    // is a racy situation anyway, this behavior seems reasonable.
    assertEquals(-1, in.read());
  }

  private static class AppendableByteSource extends ByteSource {
    private byte[] bytes;