java.lang.Integer.highestOneBit()方法的使用及代码示例

x33g5p2x  于2022-01-16 转载在 其他  
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本文整理了Java中java.lang.Integer.highestOneBit()方法的一些代码示例，展示了Integer.highestOneBit()的具体用法。这些代码示例主要来源于Github/Stackoverflow/Maven等平台，是从一些精选项目中提取出来的代码，具有较强的参考意义，能在一定程度帮忙到你。Integer.highestOneBit()方法的具体详情如下：
包路径：java.lang.Integer
类名称：Integer
方法名：highestOneBit

Integer.highestOneBit介绍

[英]Determines the highest (leftmost) bit of the specified integer that is 1 and returns the bit mask value for that bit. This is also referred to as the Most Significant 1 Bit. Returns zero if the specified integer is zero.
[中]确定指定整数的最高（最左边）位为1，并返回该位的位掩码值。这也称为最高有效1位。如果指定的整数为零，则返回零。

代码示例

代码示例来源：origin: netty/netty

  1. /**
  2.  * Calculates the minimum number of bits required to encode a value.  This can
  3.  * then in turn be used to calculate the number of septets or octets (as
  4.  * appropriate) to use to encode a length parameter.
  5.  *
  6.  * @param value The value to calculate the minimum number of bits required to encode
  7.  * @return The minimum number of bits required to encode the supplied value
  8.  */
  9. private static int bitsToEncode(int value) {
  10.   int highestOneBit = Integer.highestOneBit(value);
  11.   int bitLength = 0;
  12.   while ((highestOneBit >>= 1) != 0) {
  13.     bitLength++;
  14.   }
  15.   return bitLength;
  16. }

代码示例来源：origin: google/guava

  1. static int closedTableSize(int expectedEntries, double loadFactor) {
  2.  // Get the recommended table size.
  3.  // Round down to the nearest power of 2.
  4.  expectedEntries = Math.max(expectedEntries, 2);
  5.  int tableSize = Integer.highestOneBit(expectedEntries);
  6.  // Check to make sure that we will not exceed the maximum load factor.
  7.  if (expectedEntries > (int) (loadFactor * tableSize)) {
  8.   tableSize <<= 1;
  9.   return (tableSize > 0) ? tableSize : MAX_TABLE_SIZE;
  10.  }
  11.  return tableSize;
  12. }

代码示例来源：origin: apache/flink

  1. /**
  2.  * Decrements the given number down to the closest power of two. If the argument is a
  3.  * power of two, it remains unchanged.
  4.  *
  5.  * @param value The value to round down.
  6.  * @return The closest value that is a power of two and less or equal than the given value.
  7.  */
  8. public static int roundDownToPowerOf2(int value) {
  9.   return Integer.highestOneBit(value);
  10. }

代码示例来源：origin: prestodb/presto

  1. private static int log2Ceiling(int value)
  2. {
  3.   return Integer.highestOneBit(value - 1) << 1;
  4. }

代码示例来源：origin: google/guava

  1. private static int expandedCapacity(int oldCapacity, int minCapacity) {
  2.  if (minCapacity < 0) {
  3.   throw new AssertionError("cannot store more than MAX_VALUE elements");
  4.  }
  5.  // careful of overflow!
  6.  int newCapacity = oldCapacity + (oldCapacity >> 1) + 1;
  7.  if (newCapacity < minCapacity) {
  8.   newCapacity = Integer.highestOneBit(minCapacity - 1) << 1;
  9.  }
  10.  if (newCapacity < 0) {
  11.   newCapacity = Integer.MAX_VALUE; // guaranteed to be >= newCapacity
  12.  }
  13.  return newCapacity;
  14. }

代码示例来源：origin: google/guava

  1. private static int expandedCapacity(int oldCapacity, int minCapacity) {
  2.  if (minCapacity < 0) {
  3.   throw new AssertionError("cannot store more than MAX_VALUE elements");
  4.  }
  5.  // careful of overflow!
  6.  int newCapacity = oldCapacity + (oldCapacity >> 1) + 1;
  7.  if (newCapacity < minCapacity) {
  8.   newCapacity = Integer.highestOneBit(minCapacity - 1) << 1;
  9.  }
  10.  if (newCapacity < 0) {
  11.   newCapacity = Integer.MAX_VALUE; // guaranteed to be >= newCapacity
  12.  }
  13.  return newCapacity;
  14. }

代码示例来源：origin: google/guava

  1. private static int expandedCapacity(int oldCapacity, int minCapacity) {
  2.  if (minCapacity < 0) {
  3.   throw new AssertionError("cannot store more than MAX_VALUE elements");
  4.  }
  5.  // careful of overflow!
  6.  int newCapacity = oldCapacity + (oldCapacity >> 1) + 1;
  7.  if (newCapacity < minCapacity) {
  8.   newCapacity = Integer.highestOneBit(minCapacity - 1) << 1;
  9.  }
  10.  if (newCapacity < 0) {
  11.   newCapacity = Integer.MAX_VALUE; // guaranteed to be >= newCapacity
  12.  }
  13.  return newCapacity;
  14. }

代码示例来源：origin: google/guava

  1. static int expandedCapacity(int oldCapacity, int minCapacity) {
  2.  if (minCapacity < 0) {
  3.   throw new AssertionError("cannot store more than MAX_VALUE elements");
  4.  }
  5.  // careful of overflow!
  6.  int newCapacity = oldCapacity + (oldCapacity >> 1) + 1;
  7.  if (newCapacity < minCapacity) {
  8.   newCapacity = Integer.highestOneBit(minCapacity - 1) << 1;
  9.  }
  10.  if (newCapacity < 0) {
  11.   newCapacity = Integer.MAX_VALUE;
  12.   // guaranteed to be >= newCapacity
  13.  }
  14.  return newCapacity;
  15. }

代码示例来源：origin: bumptech/glide

  1. @Override
  2. public float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
  3.   int requestedHeight) {
  4.  int minIntegerFactor = Math.min(sourceHeight / requestedHeight, sourceWidth / requestedWidth);
  5.  return minIntegerFactor == 0 ? 1f : 1f / Integer.highestOneBit(minIntegerFactor);
  6. }

代码示例来源：origin: google/guava

  1. /**
  2.  * Returns an array size suitable for the backing array of a hash table that uses open addressing
  3.  * with linear probing in its implementation. The returned size is the smallest power of two that
  4.  * can hold setSize elements with the desired load factor.
  5.  */
  6. @VisibleForTesting
  7. static int chooseTableSize(int setSize) {
  8.  if (setSize == 1) {
  9.   return 2;
  10.  }
  11.  // Correct the size for open addressing to match desired load factor.
  12.  // Round up to the next highest power of 2.
  13.  int tableSize = Integer.highestOneBit(setSize - 1) << 1;
  14.  while (tableSize * DESIRED_LOAD_FACTOR < setSize) {
  15.   tableSize <<= 1;
  16.  }
  17.  return tableSize;
  18. }

代码示例来源：origin: prestodb/presto

  1. static int closedTableSize(int expectedEntries, double loadFactor) {
  2.  // Get the recommended table size.
  3.  // Round down to the nearest power of 2.
  4.  expectedEntries = Math.max(expectedEntries, 2);
  5.  int tableSize = Integer.highestOneBit(expectedEntries);
  6.  // Check to make sure that we will not exceed the maximum load factor.
  7.  if (expectedEntries > (int) (loadFactor * tableSize)) {
  8.   tableSize <<= 1;
  9.   return (tableSize > 0) ? tableSize : MAX_TABLE_SIZE;
  10.  }
  11.  return tableSize;
  12. }

代码示例来源：origin: bumptech/glide

  1. @Override
  2. public float getScaleFactor(int sourceWidth, int sourceHeight, int requestedWidth,
  3.   int requestedHeight) {
  4.  int maxIntegerFactor = (int) Math.ceil(Math.max(sourceHeight / (float) requestedHeight,
  5.      sourceWidth / (float) requestedWidth));
  6.  int lesserOrEqualSampleSize = Math.max(1, Integer.highestOneBit(maxIntegerFactor));
  7.  int greaterOrEqualSampleSize =
  8.    lesserOrEqualSampleSize << (lesserOrEqualSampleSize < maxIntegerFactor ? 1 : 0);
  9.  return 1f / greaterOrEqualSampleSize;
  10. }

代码示例来源：origin: google/guava

  1. /**
  2.  * Returns the largest power of two less than or equal to {@code x}. This is equivalent to {@code
  3.  * checkedPow(2, log2(x, FLOOR))}.
  4.  *
  5.  * @throws IllegalArgumentException if {@code x <= 0}
  6.  * @since 20.0
  7.  */
  8. @Beta
  9. public static int floorPowerOfTwo(int x) {
  10.  checkPositive("x", x);
  11.  return Integer.highestOneBit(x);
  12. }

代码示例来源：origin: google/guava

  1. /**
  2.  * Returns an array size suitable for the backing array of a hash table that uses open addressing
  3.  * with linear probing in its implementation. The returned size is the smallest power of two that
  4.  * can hold setSize elements with the desired load factor. Always returns at least setSize + 2.
  5.  */
  6. @VisibleForTesting
  7. static int chooseTableSize(int setSize) {
  8.  setSize = Math.max(setSize, 2);
  9.  // Correct the size for open addressing to match desired load factor.
  10.  if (setSize < CUTOFF) {
  11.   // Round up to the next highest power of 2.
  12.   int tableSize = Integer.highestOneBit(setSize - 1) << 1;
  13.   while (tableSize * DESIRED_LOAD_FACTOR < setSize) {
  14.    tableSize <<= 1;
  15.   }
  16.   return tableSize;
  17.  }
  18.  // The table can't be completely full or we'll get infinite reprobes
  19.  checkArgument(setSize < MAX_TABLE_SIZE, "collection too large");
  20.  return MAX_TABLE_SIZE;
  21. }

代码示例来源：origin: redisson/redisson

  1. public FSTIdentity2IdMap(int initialSize) {
  2.   if (initialSize < 2) {
  3.     initialSize = 2;
  4.   }
  5.   initialSize = adjustSize(initialSize * GROFAC);
  6.   mKeys = new Object[initialSize];
  7.   mValues = new int[initialSize];
  8.   mNumberOfElements = 0;
  9.   mask = (Integer.highestOneBit(initialSize) << 1) - 1;
  10.   klen = initialSize - 4;
  11. }

代码示例来源：origin: apache/incubator-druid

  1. public static int maxIntsInBufferForBytes(int numBytes)
  2. {
  3.  int maxSizePer = (CompressedPools.BUFFER_SIZE - bufferPadding(numBytes)) / numBytes;
  4.  // round down to the nearest power of 2
  5.  return Integer.highestOneBit(maxSizePer);
  6. }

代码示例来源：origin: google/guava

  1. /**
  2.  * Ensures that this {@code CompactHashMap} has the smallest representation in memory, given its
  3.  * current size.
  4.  */
  5. public void trimToSize() {
  6.  int size = this.size;
  7.  if (size < entries.length) {
  8.   resizeEntries(size);
  9.  }
  10.  // size / loadFactor gives the table size of the appropriate load factor,
  11.  // but that may not be a power of two. We floor it to a power of two by
  12.  // keeping its highest bit. But the smaller table may have a load factor
  13.  // larger than what we want; then we want to go to the next power of 2 if we can
  14.  int minimumTableSize = Math.max(1, Integer.highestOneBit((int) (size / loadFactor)));
  15.  if (minimumTableSize < MAXIMUM_CAPACITY) {
  16.   double load = (double) size / minimumTableSize;
  17.   if (load > loadFactor) {
  18.    minimumTableSize <<= 1; // increase to next power if possible
  19.   }
  20.  }
  21.  if (minimumTableSize < table.length) {
  22.   resizeTable(minimumTableSize);
  23.  }
  24. }

代码示例来源：origin: google/guava

  1. /**
  2.  * Ensures that this {@code CompactHashSet} has the smallest representation in memory, given its
  3.  * current size.
  4.  */
  5. public void trimToSize() {
  6.  int size = this.size;
  7.  if (size < entries.length) {
  8.   resizeEntries(size);
  9.  }
  10.  // size / loadFactor gives the table size of the appropriate load factor,
  11.  // but that may not be a power of two. We floor it to a power of two by
  12.  // keeping its highest bit. But the smaller table may have a load factor
  13.  // larger than what we want; then we want to go to the next power of 2 if we can
  14.  int minimumTableSize = Math.max(1, Integer.highestOneBit((int) (size / loadFactor)));
  15.  if (minimumTableSize < MAXIMUM_CAPACITY) {
  16.   double load = (double) size / minimumTableSize;
  17.   if (load > loadFactor) {
  18.    minimumTableSize <<= 1; // increase to next power if possible
  19.   }
  20.  }
  21.  if (minimumTableSize < table.length) {
  22.   resizeTable(minimumTableSize);
  23.  }
  24. }

代码示例来源：origin: prestodb/presto

  1. /**
  2.  * Returns the largest power of two less than or equal to {@code x}. This is equivalent to {@code
  3.  * checkedPow(2, log2(x, FLOOR))}.
  4.  *
  5.  * @throws IllegalArgumentException if {@code x <= 0}
  6.  * @since 20.0
  7.  */
  8. @Beta
  9. public static int floorPowerOfTwo(int x) {
  10.  checkPositive("x", x);
  11.  return Integer.highestOneBit(x);
  12. }

代码示例来源：origin: bumptech/glide

  1. private static int getSampleSize(GifHeader gifHeader, int targetWidth, int targetHeight) {
  2.  int exactSampleSize = Math.min(gifHeader.getHeight() / targetHeight,
  3.    gifHeader.getWidth() / targetWidth);
  4.  int powerOfTwoSampleSize = exactSampleSize == 0 ? 0 : Integer.highestOneBit(exactSampleSize);
  5.  // Although functionally equivalent to 0 for BitmapFactory, 1 is a safer default for our code
  6.  // than 0.
  7.  int sampleSize = Math.max(1, powerOfTwoSampleSize);
  8.  if (Log.isLoggable(TAG, Log.VERBOSE) && sampleSize > 1) {
  9.   Log.v(TAG, "Downsampling GIF"
  10.     + ", sampleSize: " + sampleSize
  11.     + ", target dimens: [" + targetWidth + "x" + targetHeight + "]"
  12.     + ", actual dimens: [" + gifHeader.getWidth() + "x" + gifHeader.getHeight() + "]");
  13.  }
  14.  return sampleSize;
  15. }

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