this.bitCount = LongAddables.create();
    }

    // Used by serialization
    LockFreeBitArray(long[] data) {
      checkArgument(data.length > 0, "data length is zero!");
      this.data = new AtomicLongArray(data);
      this.bitCount = LongAddables.create();
      long bitCount = 0;
      for (long value : data) {
        bitCount += Long.bitCount(value);
      }

   *
   * @since 22.0
   */
  public long approximateElementCount() {
    long bitSize = bits.bitSize();
    long bitCount = bits.bitCount();

    /**
     * Each insertion is expected to reduce the # of clear bits by a factor of
     * `numHashFunctions/bitSize`. So, after n insertions, expected bitCount is `bitSize * (1 - (1 -
     * numHashFunctions/bitSize)^n)`. Solving that for n, and approximating `ln x` as `x - 1` when x

    checkPositive("x", x);
    return Integer.highestOneBit(x);
  }

  /**
   * Returns {@code true} if {@code x} represents a power of two.
   *
   * <p>This differs from {@code Integer.bitCount(x) == 1}, because {@code
   * Integer.bitCount(Integer.MIN_VALUE) == 1}, but {@link Integer#MIN_VALUE} is not a power of two.
   */
  public static boolean isPowerOfTwo(int x) {
    return x > 0 & (x & (x - 1)) == 0;
  }

  /**

  public void testIsPowerOfTwo() {
    for (int x : ALL_INTEGER_CANDIDATES) {
      // Checks for a single bit set.
      BigInteger bigX = BigInteger.valueOf(x);
      boolean expected = (bigX.signum() > 0) && (bigX.bitCount() == 1);
      assertEquals(expected, IntMath.isPowerOfTwo(x));
    }
  }

  public void testLog2ZeroAlwaysThrows() {
    for (RoundingMode mode : ALL_ROUNDING_MODES) {
      try {

  public void testIsPowerOfTwo() {
    for (int x : ALL_INTEGER_CANDIDATES) {
      // Checks for a single bit set.
      BigInteger bigX = BigInteger.valueOf(x);
      boolean expected = (bigX.signum() > 0) && (bigX.bitCount() == 1);
      assertEquals(expected, IntMath.isPowerOfTwo(x));
    }
  }

  public void testLog2ZeroAlwaysThrows() {
    for (RoundingMode mode : ALL_ROUNDING_MODES) {
      try {

    return 1L << ((Long.SIZE - 1) - Long.numberOfLeadingZeros(x));
  }

  /**
   * Returns {@code true} if {@code x} represents a power of two.
   *
   * <p>This differs from {@code Long.bitCount(x) == 1}, because {@code
   * Long.bitCount(Long.MIN_VALUE) == 1}, but {@link Long#MIN_VALUE} is not a power of two.
   */
  @SuppressWarnings("ShortCircuitBoolean")
  public static boolean isPowerOfTwo(long x) {

  public void testIsPowerOfTwo() {
    for (long x : ALL_LONG_CANDIDATES) {
      // Checks for a single bit set.
      BigInteger bigX = BigInteger.valueOf(x);
      boolean expected = (bigX.signum() > 0) && (bigX.bitCount() == 1);
      assertEquals(expected, LongMath.isPowerOfTwo(x));
    }
  }

  public void testLog2ZeroAlwaysThrows() {
    for (RoundingMode mode : ALL_ROUNDING_MODES) {
      try {

  public void testIsPowerOfTwo() {
    for (long x : ALL_LONG_CANDIDATES) {
      // Checks for a single bit set.
      BigInteger bigX = BigInteger.valueOf(x);
      boolean expected = (bigX.signum() > 0) && (bigX.bitCount() == 1);
      assertEquals(expected, LongMath.isPowerOfTwo(x));
    }
  }

  public void testLog2ZeroAlwaysThrows() {
    for (RoundingMode mode : ALL_ROUNDING_MODES) {
      try {

  public long hitCount() {
    return hitCount;
  }

  /**
   * Returns the ratio of cache requests which were hits. This is defined as {@code hitCount /
   * requestCount}, or {@code 1.0} when {@code requestCount == 0}. Note that {@code hitRate +
   * missRate =~ 1.0}.
   */
  public double hitRate() {
    long requestCount = requestCount();
    return (requestCount == 0) ? 1.0 : (double) hitCount / requestCount;
  }

  public long hitCount() {
    return hitCount;
  }

  /**
   * Returns the ratio of cache requests which were hits. This is defined as {@code hitCount /
   * requestCount}, or {@code 1.0} when {@code requestCount == 0}. Note that {@code hitRate +
   * missRate =~ 1.0}.
   */
  public double hitRate() {
    long requestCount = requestCount();
    return (requestCount == 0) ? 1.0 : (double) hitCount / requestCount;
  }