public abstract long read();

  /**
   * A ticker that reads the current time using {@link System#nanoTime}.
   *
   * @since 10.0
   */
  public static Ticker systemTicker() {
    return SYSTEM_TICKER;
  }

  private static final Ticker SYSTEM_TICKER =
      new Ticker() {
        @Override
        @SuppressWarnings("GoodTime") // reading system time without TimeSource
        public long read() {

  public abstract long read();

  /**
   * A ticker that reads the current time using {@link System#nanoTime}.
   *
   * @since 10.0
   */
  public static Ticker systemTicker() {
    return SYSTEM_TICKER;
  }

  private static final Ticker SYSTEM_TICKER =
      new Ticker() {
        @Override
        @SuppressWarnings("GoodTime") // reading system time without TimeSource
        public long read() {

   *
   * @since 15.0
   */
  public static Stopwatch createStarted(Ticker ticker) {
    return new Stopwatch(ticker).start();
  }

  Stopwatch() {
    this.ticker = Ticker.systemTicker();
  }

  Stopwatch(Ticker ticker) {
    this.ticker = checkNotNull(ticker, "ticker");
  }

  /**
   * Returns {@code true} if {@link #start()} has been called on this stopwatch, and {@link #stop()}

   *
   * @since 15.0
   */
  public static Stopwatch createStarted(Ticker ticker) {
    return new Stopwatch(ticker).start();
  }

  Stopwatch() {
    this.ticker = Ticker.systemTicker();
  }

  Stopwatch(Ticker ticker) {
    this.ticker = checkNotNull(ticker, "ticker");
  }

  /**
   * Returns {@code true} if {@link #start()} has been called on this stopwatch, and {@link #stop()}

          .put(Predicate.class, Predicates.alwaysTrue())
          .put(Equivalence.class, Equivalence.equals())
          .put(Ticker.class, Ticker.systemTicker())
          .put(Stopwatch.class, Stopwatch.createUnstarted())
          // io types
          .put(InputStream.class, new ByteArrayInputStream(new byte[0]))

            0.75f,
            (builder.maximumSize != UNSET_INT),
            builder.maximumSize,
            statsCounter,
            removalListener);

    this.ticker = firstNonNull(builder.ticker, Ticker.systemTicker());
  }

  @Override
  public int size() {
    synchronized (lock) {
      return cachingHashMap.size();
    }
  }

  @Override
  public boolean isEmpty() {
    synchronized (lock) {

          .put(Predicate.class, Predicates.alwaysTrue())
          .put(Equivalence.class, Equivalence.equals())
          .put(Ticker.class, Ticker.systemTicker())
          .put(Stopwatch.class, Stopwatch.createUnstarted())
          // io types
          .put(InputStream.class, new ByteArrayInputStream(new byte[0]))

    assertThrows(IllegalStateException.class, () -> builder.refreshAfterWrite(Duration.ofHours(1)));
  }

  public void testTicker_setTwice() {
    Ticker testTicker = Ticker.systemTicker();
    CacheBuilder<Object, Object> builder = CacheBuilder.newBuilder().ticker(testTicker);
    assertThrows(IllegalStateException.class, () -> builder.ticker(testTicker));
  }

    assertThrows(IllegalStateException.class, () -> builder.refreshAfterWrite(Duration.ofHours(1)));
  }

  public void testTicker_setTwice() {
    Ticker testTicker = Ticker.systemTicker();
    CacheBuilder<Object, Object> builder = CacheBuilder.newBuilder().ticker(testTicker);
    assertThrows(IllegalStateException.class, () -> builder.ticker(testTicker));
  }

    this.ticker = checkNotNull(ticker);
    return this;
  }

  Ticker getTicker(boolean recordsTime) {
    if (ticker != null) {
      return ticker;
    }
    return recordsTime ? Ticker.systemTicker() : NULL_TICKER;
  }

  /**
   * Specifies a listener instance that caches should notify each time an entry is removed for any