private volatile long autoIncrementStepNanos;

  /** Advances the ticker value by {@code time} in {@code timeUnit}. */
  @SuppressWarnings("GoodTime") // should accept a java.time.Duration
  @CanIgnoreReturnValue
  public FakeTicker advance(long time, TimeUnit timeUnit) {
    return advance(timeUnit.toNanos(time));
  }

  /** Advances the ticker value by {@code nanoseconds}. */

  public void testElapsed_notRunning() {
    ticker.advance(1);
    stopwatch.start();
    ticker.advance(4);
    stopwatch.stop();
    ticker.advance(9);
    assertEquals(4, stopwatch.elapsed(NANOSECONDS));
  }

  public void testElapsed_multipleSegments() {
    stopwatch.start();
    ticker.advance(9);
    stopwatch.stop();

    ticker.advance(16);

    stopwatch.start();

    // 4 expires
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(6, 8, 0, 1, 2, 5, 7, 9);
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(6, 8, 0, 1, 2, 5, 7, 9);

    // 6 expires
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(8, 0, 1, 2, 5, 7, 9);
    ticker.advance(1, MILLISECONDS);

    cache.asMap().put(1, -1);
    ticker.advance(1, MILLISECONDS);
    assertEquals(Integer.valueOf(1), cache.getUnchecked(0));
    assertEquals(Integer.valueOf(-1), cache.getUnchecked(1));
    assertEquals(Integer.valueOf(2), cache.getUnchecked(2));
    assertEquals(expectedLoads, loader.getLoadCount());
    assertEquals(expectedReloads, loader.getReloadCount());

    // refresh 2
    ticker.advance(1, MILLISECONDS);

  public void testElapsed_notRunning() {
    ticker.advance(1);
    stopwatch.start();
    ticker.advance(4);
    stopwatch.stop();
    ticker.advance(9);
    assertEquals(4, stopwatch.elapsed(NANOSECONDS));
  }

  public void testElapsed_multipleSegments() {
    stopwatch.start();
    ticker.advance(9);
    stopwatch.stop();

    ticker.advance(16);

    stopwatch.start();

  public void testAdvance() {
    FakeTicker ticker = new FakeTicker();
    assertEquals(0, ticker.read());
    assertSame(ticker, ticker.advance(10));
    assertEquals(10, ticker.read());
    ticker.advance(1, TimeUnit.MILLISECONDS);
    assertEquals(1000010L, ticker.read());
    ticker.advance(Duration.ofMillis(1));
    assertEquals(2000010L, ticker.read());
  }

  public void testAutoIncrementStep_returnsSameInstance() {

    // 4 expires
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(6, 8, 0, 1, 2, 5, 7, 9);
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(6, 8, 0, 1, 2, 5, 7, 9);

    // 6 expires
    ticker.advance(1, MILLISECONDS);
    assertThat(keySet).containsExactly(8, 0, 1, 2, 5, 7, 9);
    ticker.advance(1, MILLISECONDS);

    assertEquals(0, stats.hitCount());

    ticker.advance(1, MILLISECONDS);
    assertSame(one, cache.getUnchecked(key));
    stats = cache.stats();
    assertEquals(1, stats.missCount());
    assertEquals(1, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());
    assertEquals(1, stats.hitCount());

    ticker.advance(1, MILLISECONDS);
    assertSame(two, cache.getUnchecked(key));

  @CheckForNull private Reader current;

  MultiReader(Iterator<? extends CharSource> readers) throws IOException {
    this.it = readers;
    advance();
  }

  /** Closes the current reader and opens the next one, if any. */
  private void advance() throws IOException {
    close();
    if (it.hasNext()) {
      current = it.next().openStream();
    }
  }

  @Override

    this.it = checkNotNull(it);
    advance();
  }

  @Override
  public void close() throws IOException {
    if (in != null) {
      try {
        in.close();
      } finally {
        in = null;
      }
    }
  }

  /** Closes the current input stream and opens the next one, if any. */
  private void advance() throws IOException {
    close();
    if (it.hasNext()) {