* versions.
   */
  public static Stats fromByteArray(byte[] byteArray) {
    checkNotNull(byteArray);
    checkArgument(
        byteArray.length == BYTES,
        "Expected Stats.BYTES = %s remaining , got %s",
        BYTES,
        byteArray.length);
    return readFrom(ByteBuffer.wrap(byteArray).order(ByteOrder.LITTLE_ENDIAN));
  }

  /**

    stats = cache.stats();
    assertEquals(2, stats.missCount());
    assertEquals(3, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());
    assertEquals(0, stats.hitCount());

    assertSame(key, cache.get(key));
    stats = cache.stats();
    assertEquals(2, stats.missCount());
    assertEquals(3, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());

    assertStatsApproxEqual(TWO_VALUES_STATS, TWO_VALUES_PAIRED_STATS.xStats());
    assertStatsApproxEqual(MANY_VALUES_STATS_ITERABLE, MANY_VALUES_PAIRED_STATS.xStats());
  }

  public void testYStats() {
    assertStatsApproxEqual(EMPTY_STATS_ITERABLE, EMPTY_PAIRED_STATS.yStats());
    assertStatsApproxEqual(OTHER_ONE_VALUE_STATS, ONE_VALUE_PAIRED_STATS.yStats());

    assertStatsApproxEqual(TWO_VALUES_STATS, TWO_VALUES_PAIRED_STATS.xStats());
    assertStatsApproxEqual(MANY_VALUES_STATS_ITERABLE, MANY_VALUES_PAIRED_STATS.xStats());
  }

  public void testYStats() {
    assertStatsApproxEqual(EMPTY_STATS_ITERABLE, EMPTY_PAIRED_STATS.yStats());
    assertStatsApproxEqual(OTHER_ONE_VALUE_STATS, ONE_VALUE_PAIRED_STATS.yStats());

    Stats stats = Stats.of(megaPrimitiveDoubleStream());
    assertThat(stats.count()).isEqualTo(MEGA_STREAM_COUNT);
    assertThat(stats.mean()).isWithin(ALLOWED_ERROR * MEGA_STREAM_COUNT).of(MEGA_STREAM_MEAN);
    assertThat(stats.populationVariance())
        .isWithin(ALLOWED_ERROR * MEGA_STREAM_COUNT)
        .of(MEGA_STREAM_POPULATION_VARIANCE);
    assertThat(stats.min()).isEqualTo(MEGA_STREAM_MIN);

  public void testEmpty() {
    CacheStats stats = new CacheStats(0, 0, 0, 0, 0, 0);
    assertEquals(0, stats.requestCount());
    assertEquals(0, stats.hitCount());
    assertEquals(1.0, stats.hitRate());
    assertEquals(0, stats.missCount());
    assertEquals(0.0, stats.missRate());
    assertEquals(0, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());
    assertEquals(0.0, stats.loadExceptionRate());

/**
 * Tests for {@link StatsAccumulator}. This tests the stats methods for instances built with {@link
 * StatsAccumulator#add} and {@link StatsAccumulator#addAll}, and various error cases of the {@link
 * StatsAccumulator#add} and {@link StatsAccumulator#addAll} methods. For tests of the {@link
 * StatsAccumulator#snapshot} method which returns {@link Stats} instances, see {@link StatsTest}.
 *
 * @author Pete Gillin
 */

    assertEquals(1, stats.hitCount());
    assertEquals(1.0 / 2, stats.hitRate());
    assertEquals(1, stats.missCount());
    assertEquals(1.0 / 2, stats.missRate());
    assertEquals(1, stats.loadCount());
    assertEquals(0, stats.evictionCount());

    Object two = new Object();
    cache.getUnchecked(two);
    stats = cache.stats();
    assertEquals(3, stats.requestCount());

    stats = cache.stats();
    assertEquals(2, stats.missCount());
    assertEquals(3, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());
    assertEquals(0, stats.hitCount());

    assertSame(key, cache.get(key));
    stats = cache.stats();
    assertEquals(2, stats.missCount());
    assertEquals(3, stats.loadSuccessCount());
    assertEquals(0, stats.loadExceptionCount());

        .addEqualityGroup(
            Stats.of(1.0, 1.0, 5.0, 5.0),
            Stats.of(1.0, 1.0, 5.0, 5.0),
            Stats.of(ImmutableList.of(1.0, 1.0, 5.0, 5.0)),
            Stats.of(ImmutableList.of(1.0, 1.0, 5.0, 5.0).iterator()),
            SerializableTester.reserialize(Stats.of(1.0, 1.0, 5.0, 5.0)))
        .addEqualityGroup(Stats.of(1.0, 5.0))
        .addEqualityGroup(Stats.of(1.0, 5.0, 1.0, 6.0))