Class BitSet
- All Implemented Interfaces:
- Serializable,- Cloneable
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.
- Since:
- 1.0
- See Also:
- 
Constructor SummaryConstructors
- 
Method SummaryModifier and TypeMethodDescriptionvoidPerforms a logical AND of this target bit set with the argument bit set.voidClears all of the bits in thisBitSetwhose corresponding bit is set in the specifiedBitSet.intReturns the number of bits set totruein thisBitSet.voidclear()Sets all of the bits in this BitSet tofalse.voidclear(int bitIndex) Sets the bit specified by the index tofalse.voidclear(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex(inclusive) to the specifiedtoIndex(exclusive) tofalse.clone()Cloning thisBitSetproduces a newBitSetthat is equal to it.booleanCompares this bit set against the specified object.voidflip(int bitIndex) Sets the bit at the specified index to the complement of its current value.voidflip(int fromIndex, int toIndex) Sets each bit from the specifiedfromIndex(inclusive) to the specifiedtoIndex(exclusive) to the complement of its current value.booleanget(int bitIndex) Returns the value of the bit with the specified index.get(int fromIndex, int toIndex) Returns a newBitSetcomposed of bits from thisBitSetfromfromIndex(inclusive) totoIndex(exclusive).inthashCode()Returns the hash code value for this bit set.booleanintersects(BitSet set) Returns true if the specifiedBitSethas any bits set totruethat are also set totruein thisBitSet.booleanisEmpty()Returns true if thisBitSetcontains no bits that are set totrue.intlength()Returns the "logical size" of thisBitSet: the index of the highest set bit in theBitSetplus one.intnextClearBit(int fromIndex) Returns the index of the first bit that is set tofalsethat occurs on or after the specified starting index.intnextSetBit(int fromIndex) Returns the index of the first bit that is set totruethat occurs on or after the specified starting index.voidPerforms a logical OR of this bit set with the bit set argument.intpreviousClearBit(int fromIndex) Returns the index of the nearest bit that is set tofalsethat occurs on or before the specified starting index.intpreviousSetBit(int fromIndex) Returns the index of the nearest bit that is set totruethat occurs on or before the specified starting index.voidset(int bitIndex) Sets the bit at the specified index totrue.voidset(int bitIndex, boolean value) Sets the bit at the specified index to the specified value.voidset(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex(inclusive) to the specifiedtoIndex(exclusive) totrue.voidset(int fromIndex, int toIndex, boolean value) Sets the bits from the specifiedfromIndex(inclusive) to the specifiedtoIndex(exclusive) to the specified value.intsize()Returns the number of bits of space actually in use by thisBitSetto represent bit values.stream()Returns a stream of indices for which thisBitSetcontains a bit in the set state.byte[]Returns a new byte array containing all the bits in this bit set.long[]Returns a new long array containing all the bits in this bit set.toString()Returns a string representation of this bit set.static BitSetvalueOf(byte[] bytes) Returns a new bit set containing all the bits in the given byte array.static BitSetvalueOf(long[] longs) Returns a new bit set containing all the bits in the given long array.static BitSetvalueOf(ByteBuffer bb) Returns a new bit set containing all the bits in the given byte buffer between its position and limit.static BitSetvalueOf(LongBuffer lb) Returns a new bit set containing all the bits in the given long buffer between its position and limit.voidPerforms a logical XOR of this bit set with the bit set argument.
- 
Constructor Details- 
BitSetpublic BitSet()Creates a new bit set. All bits are initiallyfalse.
- 
BitSetpublic BitSet(int nbits) Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range0throughnbits-1. All bits are initiallyfalse.- Parameters:
- nbits- the initial size of the bit set
- Throws:
- NegativeArraySizeException- if the specified initial size is negative
 
 
- 
- 
Method Details- 
valueOfReturns 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 alln < 64 * longs.length.This method is equivalent to BitSet.valueOf(LongBuffer.wrap(longs)).- Parameters:
- 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 set
- Returns:
- a BitSetcontaining all the bits in the long array
- Since:
- 1.7
 
- 
valueOfReturns 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 alln < 64 * lb.remaining().The long buffer is not modified by this method, and no reference to the buffer is retained by the bit set. - Parameters:
- 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 set
- Returns:
- a BitSetcontaining all the bits in the buffer in the specified range
- Since:
- 1.7
 
- 
valueOfReturns 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 alln < 8 * bytes.length.This method is equivalent to BitSet.valueOf(ByteBuffer.wrap(bytes)).- Parameters:
- 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 set
- Returns:
- a BitSetcontaining all the bits in the byte array
- Since:
- 1.7
 
- 
valueOfReturns 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 alln < 8 * bb.remaining().The byte buffer is not modified by this method, and no reference to the buffer is retained by the bit set. - Parameters:
- 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 set
- Returns:
- a BitSetcontaining all the bits in the buffer in the specified range
- Since:
- 1.7
 
- 
toByteArraypublic byte[] toByteArray()Returns a new byte array containing all the bits in this bit set.More precisely, if byte[] bytes = s.toByteArray();
 thenbytes.length == (s.length()+7)/8ands.get(n) == ((bytes[n/8] & (1<<(n%8))) != 0)
 for alln < 8 * bytes.length.- Returns:
- a byte array containing a little-endian representation of all the bits in this bit set
- Since:
- 1.7
 
- 
toLongArraypublic long[] toLongArray()Returns a new long array containing all the bits in this bit set.More precisely, if long[] longs = s.toLongArray();
 thenlongs.length == (s.length()+63)/64ands.get(n) == ((longs[n/64] & (1L<<(n%64))) != 0)
 for alln < 64 * longs.length.- Returns:
- a long array containing a little-endian representation of all the bits in this bit set
- Since:
- 1.7
 
- 
flippublic void flip(int bitIndex) Sets the bit at the specified index to the complement of its current value.- Parameters:
- bitIndex- the index of the bit to flip
- Throws:
- IndexOutOfBoundsException- if the specified index is negative
- Since:
- 1.4
 
- 
flippublic void flip(int fromIndex, int toIndex) Sets each bit from the specifiedfromIndex(inclusive) to the specifiedtoIndex(exclusive) to the complement of its current value.- Parameters:
- fromIndex- index of the first bit to flip
- toIndex- index after the last bit to flip
- Throws:
- IndexOutOfBoundsException- if- fromIndexis negative, or- toIndexis negative, or- fromIndexis larger than- toIndex
- Since:
- 1.4
 
- 
setpublic void set(int bitIndex) Sets the bit at the specified index totrue.- Parameters:
- bitIndex- a bit index
- Throws:
- IndexOutOfBoundsException- if the specified index is negative
- Since:
- 1.0
 
- 
setpublic void set(int bitIndex, boolean value) Sets the bit at the specified index to the specified value.- Parameters:
- bitIndex- a bit index
- value- a boolean value to set
- Throws:
- IndexOutOfBoundsException- if the specified index is negative
- Since:
- 1.4
 
- 
setpublic void set(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex(inclusive) to the specifiedtoIndex(exclusive) totrue.- Parameters:
- fromIndex- index of the first bit to be set
- toIndex- index after the last bit to be set
- Throws:
- IndexOutOfBoundsException- if- fromIndexis negative, or- toIndexis negative, or- fromIndexis larger than- toIndex
- Since:
- 1.4
 
- 
setpublic void set(int fromIndex, int toIndex, boolean value) Sets the bits from the specifiedfromIndex(inclusive) to the specifiedtoIndex(exclusive) to the specified value.- Parameters:
- fromIndex- index of the first bit to be set
- toIndex- index after the last bit to be set
- value- value to set the selected bits to
- Throws:
- IndexOutOfBoundsException- if- fromIndexis negative, or- toIndexis negative, or- fromIndexis larger than- toIndex
- Since:
- 1.4
 
- 
clearpublic void clear(int bitIndex) Sets the bit specified by the index tofalse.- Parameters:
- bitIndex- the index of the bit to be cleared
- Throws:
- IndexOutOfBoundsException- if the specified index is negative
- Since:
- 1.0
 
- 
clearpublic void clear(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex(inclusive) to the specifiedtoIndex(exclusive) tofalse.- Parameters:
- fromIndex- index of the first bit to be cleared
- toIndex- index after the last bit to be cleared
- Throws:
- IndexOutOfBoundsException- if- fromIndexis negative, or- toIndexis negative, or- fromIndexis larger than- toIndex
- Since:
- 1.4
 
- 
clearpublic void clear()Sets all of the bits in this BitSet tofalse.- Since:
- 1.4
 
- 
getpublic boolean get(int bitIndex) Returns the value of the bit with the specified index. The value istrueif the bit with the indexbitIndexis currently set in thisBitSet; otherwise, the result isfalse.- Parameters:
- bitIndex- the bit index
- Returns:
- the value of the bit with the specified index
- Throws:
- IndexOutOfBoundsException- if the specified index is negative
 
- 
getReturns a newBitSetcomposed of bits from thisBitSetfromfromIndex(inclusive) totoIndex(exclusive).- Parameters:
- fromIndex- index of the first bit to include
- toIndex- index after the last bit to include
- Returns:
- a new BitSetfrom a range of thisBitSet
- Throws:
- IndexOutOfBoundsException- if- fromIndexis negative, or- toIndexis negative, or- fromIndexis larger than- toIndex
- Since:
- 1.4
 
- 
nextSetBitpublic int nextSetBit(int fromIndex) Returns the index of the first bit that is set totruethat occurs on or after the specified starting index. If no such bit exists then-1is returned.To iterate over the truebits in aBitSet, 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 } }- Parameters:
- fromIndex- the index to start checking from (inclusive)
- Returns:
- the index of the next set bit, or -1if there is no such bit
- Throws:
- IndexOutOfBoundsException- if the specified index is negative
- Since:
- 1.4
 
- 
nextClearBitpublic int nextClearBit(int fromIndex) Returns the index of the first bit that is set tofalsethat occurs on or after the specified starting index.- Parameters:
- fromIndex- the index to start checking from (inclusive)
- Returns:
- the index of the next clear bit
- Throws:
- IndexOutOfBoundsException- if the specified index is negative
- Since:
- 1.4
 
- 
previousSetBitpublic int previousSetBit(int fromIndex) Returns the index of the nearest bit that is set totruethat occurs on or before the specified starting index. If no such bit exists, or if-1is given as the starting index, then-1is returned.To iterate over the truebits in aBitSet, use the following loop:for (int i = bs.length(); (i = bs.previousSetBit(i-1)) >= 0; ) { // operate on index i here }- Parameters:
- fromIndex- the index to start checking from (inclusive)
- Returns:
- the index of the previous set bit, or -1if there is no such bit
- Throws:
- IndexOutOfBoundsException- if the specified index is less than- -1
- Since:
- 1.7
 
- 
previousClearBitpublic int previousClearBit(int fromIndex) Returns the index of the nearest bit that is set tofalsethat occurs on or before the specified starting index. If no such bit exists, or if-1is given as the starting index, then-1is returned.- Parameters:
- fromIndex- the index to start checking from (inclusive)
- Returns:
- the index of the previous clear bit, or -1if there is no such bit
- Throws:
- IndexOutOfBoundsException- if the specified index is less than- -1
- Since:
- 1.7
 
- 
lengthpublic int length()Returns the "logical size" of thisBitSet: the index of the highest set bit in theBitSetplus one. Returns zero if theBitSetcontains no set bits.- Returns:
- the logical size of this BitSet
- Since:
- 1.2
 
- 
isEmptypublic boolean isEmpty()Returns true if thisBitSetcontains no bits that are set totrue.- Returns:
- boolean indicating whether this BitSetis empty
- Since:
- 1.4
 
- 
intersectsReturns true if the specifiedBitSethas any bits set totruethat are also set totruein thisBitSet.- Parameters:
- set-- BitSetto intersect with
- Returns:
- boolean indicating whether this BitSetintersects the specifiedBitSet
- Since:
- 1.4
 
- 
cardinalitypublic int cardinality()Returns the number of bits set totruein thisBitSet.- Returns:
- the number of bits set to truein thisBitSet
- Since:
- 1.4
 
- 
andPerforms 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 valuetrueif and only if it both initially had the valuetrueand the corresponding bit in the bit set argument also had the valuetrue.- Parameters:
- set- a bit set
 
- 
orPerforms 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 valuetrueif and only if it either already had the valuetrueor the corresponding bit in the bit set argument has the valuetrue.- Parameters:
- set- a bit set
 
- 
xorPerforms 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 valuetrueif and only if one of the following statements holds:- The bit initially has the value true, and the corresponding bit in the argument has the valuefalse.
- The bit initially has the value false, and the corresponding bit in the argument has the valuetrue.
 - Parameters:
- set- a bit set
 
- The bit initially has the value 
- 
andNotClears all of the bits in thisBitSetwhose corresponding bit is set in the specifiedBitSet.- Parameters:
- set- the- BitSetwith which to mask this- BitSet
- Since:
- 1.2
 
- 
hashCodepublic int hashCode()Returns the hash code value for this bit set. The hash code depends only on which bits are set within thisBitSet.The hash code is defined to be the result of the following calculation: 
 Note that the hash code changes if the set of bits is altered.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); }
- 
sizepublic int size()Returns the number of bits of space actually in use by thisBitSetto represent bit values. The maximum element in the set is the size - 1st element.- Returns:
- the number of bits currently in this bit set
 
- 
equalsCompares this bit set against the specified object. The result istrueif and only if the argument is notnulland is aBitSetobject that has exactly the same set of bits set totrueas this bit set. That is, for every nonnegativeintindexk,((BitSet)obj).get(k) == this.get(k) must be true. The current sizes of the two bit sets are not compared.
- 
clone
- 
toStringReturns a string representation of this bit set. For every index for which thisBitSetcontains 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(); NowdrPepper.toString()returns "{}".drPepper.set(2); NowdrPepper.toString()returns "{2}".drPepper.set(4); drPepper.set(10); NowdrPepper.toString()returns "{2, 4, 10}".
- 
streamReturns a stream of indices for which thisBitSetcontains 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 thecardinality()method.The stream binds to this bit set when the terminal stream operation commences (specifically, the spliterator for the stream is late-binding). If the bit set is modified during that operation then the result is undefined. - Returns:
- a stream of integers representing set indices
- Since:
- 1.8
 
 
-