public class BitSet extends Object implements Cloneable, Serializable
This class implements a vector of bits that grows as needed. Each component of the bit set has a boolean value. The bits of a BitSet are indexed by nonnegative integers. Individual indexed bits can be examined, set, or cleared. One BitSet may be used to modify the contents of another BitSet through logical AND, logical inclusive OR, and logical exclusive OR operations.
By default, all bits in the set initially have the value false.
Every bit set has a current size, which is the number of bits of space currently in use by the bit set. Note that the size is related to the implementation of a bit set, so it may change with implementation. The length of a bit set relates to logical length of a bit set and is defined independently of implementation.
Unless otherwise noted, passing a null parameter to any of the methods in a BitSet will result in a NullPointerException.
A BitSet is not safe for multithreaded use without external synchronization.
public BitSet()
Creates a new bit set. All bits are initially false.
public BitSet(int nbits)
Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range 0 through nbits-1. All bits are initially false.
nbits - the initial size of the bit setNegativeArraySizeException - if the specified initial size is negativepublic static BitSet valueOf(long[] longs)
Returns a new bit set containing all the bits in the given long array.
More precisely, BitSet.valueOf(longs).get(n) == ((longs[n/64] & (1L<<(n%64))) != 0)
for all n < 64 * longs.length.
This method is equivalent to BitSet.valueOf(LongBuffer.wrap(longs)).
longs - a long array containing a little-endian representation of a sequence of bits to be used as the initial bits of the new bit setBitSet containing all the bits in the long arraypublic static BitSet valueOf(LongBuffer lb)
Returns a new bit set containing all the bits in the given long buffer between its position and limit.
More precisely, BitSet.valueOf(lb).get(n) == ((lb.get(lb.position()+n/64) & (1L<<(n%64))) != 0)
for all n < 64 * lb.remaining().
The long buffer is not modified by this method, and no reference to the buffer is retained by the bit set.
lb - a long buffer containing a little-endian representation of a sequence of bits between its position and limit, to be used as the initial bits of the new bit setBitSet containing all the bits in the buffer in the specified rangepublic static BitSet valueOf(byte[] bytes)
Returns a new bit set containing all the bits in the given byte array.
More precisely, BitSet.valueOf(bytes).get(n) == ((bytes[n/8] & (1<<(n%8))) != 0)
for all n < 8 * bytes.length.
This method is equivalent to BitSet.valueOf(ByteBuffer.wrap(bytes)).
bytes - a byte array containing a little-endian representation of a sequence of bits to be used as the initial bits of the new bit setBitSet containing all the bits in the byte arraypublic static BitSet valueOf(ByteBuffer bb)
Returns a new bit set containing all the bits in the given byte buffer between its position and limit.
More precisely, BitSet.valueOf(bb).get(n) == ((bb.get(bb.position()+n/8) & (1<<(n%8))) != 0)
for all n < 8 * bb.remaining().
The byte buffer is not modified by this method, and no reference to the buffer is retained by the bit set.
bb - a byte buffer containing a little-endian representation of a sequence of bits between its position and limit, to be used as the initial bits of the new bit setBitSet containing all the bits in the buffer in the specified rangepublic byte[] toByteArray()
Returns a new byte array containing all the bits in this bit set.
More precisely, if byte[] bytes = s.toByteArray();
then bytes.length == (s.length()+7)/8 and s.get(n) == ((bytes[n/8] & (1<<(n%8))) != 0)
for all n < 8 * bytes.length.
public long[] toLongArray()
Returns a new long array containing all the bits in this bit set.
More precisely, if long[] longs = s.toLongArray();
then longs.length == (s.length()+63)/64 and s.get(n) == ((longs[n/64] & (1L<<(n%64))) != 0)
for all n < 64 * longs.length.
public void flip(int bitIndex)
Sets the bit at the specified index to the complement of its current value.
bitIndex - the index of the bit to flipIndexOutOfBoundsException - if the specified index is negativepublic void flip(int fromIndex,
int toIndex) Sets each bit from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to the complement of its current value.
fromIndex - index of the first bit to fliptoIndex - index after the last bit to flipIndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex
public void set(int bitIndex)
Sets the bit at the specified index to true.
bitIndex - a bit indexIndexOutOfBoundsException - if the specified index is negativepublic void set(int bitIndex,
boolean value) Sets the bit at the specified index to the specified value.
bitIndex - a bit indexvalue - a boolean value to setIndexOutOfBoundsException - if the specified index is negativepublic void set(int fromIndex,
int toIndex) Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to true.
fromIndex - index of the first bit to be settoIndex - index after the last bit to be setIndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex
public void set(int fromIndex,
int toIndex,
boolean value) Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to the specified value.
fromIndex - index of the first bit to be settoIndex - index after the last bit to be setvalue - value to set the selected bits toIndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex
public void clear(int bitIndex)
Sets the bit specified by the index to false.
bitIndex - the index of the bit to be clearedIndexOutOfBoundsException - if the specified index is negativepublic void clear(int fromIndex,
int toIndex) Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to false.
fromIndex - index of the first bit to be clearedtoIndex - index after the last bit to be clearedIndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex
public void clear()
Sets all of the bits in this BitSet to false.
public boolean get(int bitIndex)
Returns the value of the bit with the specified index. The value is true if the bit with the index bitIndex is currently set in this BitSet; otherwise, the result is false.
bitIndex - the bit indexIndexOutOfBoundsException - if the specified index is negativepublic BitSet get(int fromIndex,
int toIndex) Returns a new BitSet composed of bits from this BitSet from fromIndex (inclusive) to toIndex (exclusive).
fromIndex - index of the first bit to includetoIndex - index after the last bit to includeBitSet from a range of this BitSet
IndexOutOfBoundsException - if fromIndex is negative, or toIndex is negative, or fromIndex is larger than toIndex
public int nextSetBit(int fromIndex)
Returns the index of the first bit that is set to true that occurs on or after the specified starting index. If no such bit exists then -1 is returned.
To iterate over the true bits in a BitSet, use the following loop:
for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i+1)) {
// operate on index i here
if (i == Integer.MAX_VALUE) {
break; // or (i+1) would overflow
}
}
fromIndex - the index to start checking from (inclusive)-1 if there is no such bitIndexOutOfBoundsException - if the specified index is negativepublic int nextClearBit(int fromIndex)
Returns the index of the first bit that is set to false that occurs on or after the specified starting index.
fromIndex - the index to start checking from (inclusive)IndexOutOfBoundsException - if the specified index is negativepublic int previousSetBit(int fromIndex)
Returns the index of the nearest bit that is set to true that occurs on or before the specified starting index. If no such bit exists, or if -1 is given as the starting index, then -1 is returned.
To iterate over the true bits in a BitSet, use the following loop:
for (int i = bs.length(); (i = bs.previousSetBit(i-1)) >= 0; ) {
// operate on index i here
}
fromIndex - the index to start checking from (inclusive)-1 if there is no such bitIndexOutOfBoundsException - if the specified index is less than -1
public int previousClearBit(int fromIndex)
Returns the index of the nearest bit that is set to false that occurs on or before the specified starting index. If no such bit exists, or if -1 is given as the starting index, then -1 is returned.
fromIndex - the index to start checking from (inclusive)-1 if there is no such bitIndexOutOfBoundsException - if the specified index is less than -1
public int length()
Returns the "logical size" of this BitSet: the index of the highest set bit in the BitSet plus one. Returns zero if the BitSet contains no set bits.
BitSet
public boolean isEmpty()
Returns true if this BitSet contains no bits that are set to true.
BitSet is emptypublic boolean intersects(BitSet set)
Returns true if the specified BitSet has any bits set to true that are also set to true in this BitSet.
set - BitSet to intersect withBitSet intersects the specified BitSet
public int cardinality()
Returns the number of bits set to true in this BitSet.
true in this BitSet
public void and(BitSet set)
Performs a logical AND of this target bit set with the argument bit set. This bit set is modified so that each bit in it has the value true if and only if it both initially had the value true and the corresponding bit in the bit set argument also had the value true.
set - a bit setpublic void or(BitSet set)
Performs a logical OR of this bit set with the bit set argument. This bit set is modified so that a bit in it has the value true if and only if it either already had the value true or the corresponding bit in the bit set argument has the value true.
set - a bit setpublic void xor(BitSet set)
Performs a logical XOR of this bit set with the bit set argument. This bit set is modified so that a bit in it has the value true if and only if one of the following statements holds:
true, and the corresponding bit in the argument has the value false. false, and the corresponding bit in the argument has the value true. set - a bit setpublic void andNot(BitSet set)
Clears all of the bits in this BitSet whose corresponding bit is set in the specified BitSet.
set - the BitSet with which to mask this BitSet
public int hashCode()
Returns the hash code value for this bit set. The hash code depends only on which bits are set within this BitSet.
The hash code is defined to be the result of the following calculation:
public int hashCode() {
long h = 1234;
long[] words = toLongArray();
for (int i = words.length; --i >= 0; )
h ^= words[i] * (i + 1);
return (int)((h >> 32) ^ h);
} Note that the hash code changes if the set of bits is altered.hashCode in class Object
Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)
public int size()
Returns the number of bits of space actually in use by this BitSet to represent bit values. The maximum element in the set is the size - 1st element.
public boolean equals(Object obj)
Compares this object against the specified object. The result is true if and only if the argument is not null and is a Bitset object that has exactly the same set of bits set to true as this bit set. That is, for every nonnegative int index k,
((BitSet)obj).get(k) == this.get(k)must be true. The current sizes of the two bit sets are not compared.
equals in class Object
obj - the object to compare withtrue if the objects are the same; false otherwisesize()public Object clone()
Cloning this BitSet produces a new BitSet that is equal to it. The clone of the bit set is another bit set that has exactly the same bits set to true as this bit set.
public String toString()
Returns a string representation of this bit set. For every index for which this BitSet contains a bit in the set state, the decimal representation of that index is included in the result. Such indices are listed in order from lowest to highest, separated by ", " (a comma and a space) and surrounded by braces, resulting in the usual mathematical notation for a set of integers.
Example:
BitSet drPepper = new BitSet();Now
drPepper.toString() returns "{}". drPepper.set(2);Now
drPepper.toString() returns "{2}". drPepper.set(4); drPepper.set(10);Now
drPepper.toString() returns "{2, 4, 10}".public IntStream stream()
Returns a stream of indices for which this BitSet contains a bit in the set state. The indices are returned in order, from lowest to highest. The size of the stream is the number of bits in the set state, equal to the value returned by the cardinality() method.
The bit set must remain constant during the execution of the terminal stream operation. Otherwise, the result of the terminal stream operation is undefined.
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