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 Summary

Method Summary
Modifier and TypeMethodDescriptionvoid
Performs a logical AND of this target bit set with the argument bit set.void
Clears all of the bits in thisBitSet
whose corresponding bit is set in the specifiedBitSet
.int
Returns the number of bits set totrue
in thisBitSet
.void
clear()
Sets all of the bits in this BitSet tofalse
.void
clear
(int bitIndex) Sets the bit specified by the index tofalse
.void
clear
(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex
(inclusive) to the specifiedtoIndex
(exclusive) tofalse
.clone()
Cloning thisBitSet
produces a newBitSet
that is equal to it.boolean
Compares this bit set against the specified object.void
flip
(int bitIndex) Sets the bit at the specified index to the complement of its current value.void
flip
(int fromIndex, int toIndex) Sets each bit from the specifiedfromIndex
(inclusive) to the specifiedtoIndex
(exclusive) to the complement of its current value.boolean
get
(int bitIndex) Returns the value of the bit with the specified index.get
(int fromIndex, int toIndex) Returns a newBitSet
composed of bits from thisBitSet
fromfromIndex
(inclusive) totoIndex
(exclusive).int
hashCode()
Returns the hash code value for this bit set.boolean
intersects
(BitSet set) Returns true if the specifiedBitSet
has any bits set totrue
that are also set totrue
in thisBitSet
.boolean
isEmpty()
Returns true if thisBitSet
contains no bits that are set totrue
.int
length()
Returns the "logical size" of thisBitSet
: the index of the highest set bit in theBitSet
plus one.int
nextClearBit
(int fromIndex) Returns the index of the first bit that is set tofalse
that occurs on or after the specified starting index.int
nextSetBit
(int fromIndex) Returns the index of the first bit that is set totrue
that occurs on or after the specified starting index.void
Performs a logical OR of this bit set with the bit set argument.int
previousClearBit
(int fromIndex) Returns the index of the nearest bit that is set tofalse
that occurs on or before the specified starting index.int
previousSetBit
(int fromIndex) Returns the index of the nearest bit that is set totrue
that occurs on or before the specified starting index.void
set
(int bitIndex) Sets the bit at the specified index totrue
.void
set
(int bitIndex, boolean value) Sets the bit at the specified index to the specified value.void
set
(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex
(inclusive) to the specifiedtoIndex
(exclusive) totrue
.void
set
(int fromIndex, int toIndex, boolean value) Sets the bits from the specifiedfromIndex
(inclusive) to the specifiedtoIndex
(exclusive) to the specified value.int
size()
Returns the number of bits of space actually in use by thisBitSet
to represent bit values.stream()
Returns a stream of indices for which thisBitSet
contains 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 BitSet
valueOf
(byte[] bytes) Returns a new bit set containing all the bits in the given byte array.static BitSet
valueOf
(long[] longs) Returns a new bit set containing all the bits in the given long array.static BitSet
valueOf
(ByteBuffer bb) Returns a new bit set containing all the bits in the given byte buffer between its position and limit.static BitSet
valueOf
(LongBuffer lb) Returns a new bit set containing all the bits in the given long buffer between its position and limit.void
Performs a logical XOR of this bit set with the bit set argument.

Constructor Details

BitSet
public BitSet()Creates a new bit set. All bits are initiallyfalse
. 
BitSet
public BitSet(int nbits) Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range0
throughnbits1
. All bits are initiallyfalse
. Parameters:
nbits
 the initial size of the bit set Throws:
NegativeArraySizeException
 if the specified initial size is negative


Method Details

valueOf
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 alln < 64 * longs.length
.This method is equivalent to
BitSet.valueOf(LongBuffer.wrap(longs))
. Parameters:
longs
 a long array containing a littleendian representation of a sequence of bits to be used as the initial bits of the new bit set Returns:
 a
BitSet
containing all the bits in the long array  Since:
 1.7

valueOf
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 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 littleendian 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
BitSet
containing all the bits in the buffer in the specified range  Since:
 1.7

valueOf
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 alln < 8 * bytes.length
.This method is equivalent to
BitSet.valueOf(ByteBuffer.wrap(bytes))
. Parameters:
bytes
 a byte array containing a littleendian representation of a sequence of bits to be used as the initial bits of the new bit set Returns:
 a
BitSet
containing all the bits in the byte array  Since:
 1.7

valueOf
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 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 littleendian 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
BitSet
containing all the bits in the buffer in the specified range  Since:
 1.7

toByteArray
public 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)/8
ands.get(n) == ((bytes[n/8] & (1<<(n%8))) != 0)
for alln < 8 * bytes.length
. Returns:
 a byte array containing a littleendian representation of all the bits in this bit set
 Since:
 1.7

toLongArray
public 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)/64
ands.get(n) == ((longs[n/64] & (1L<<(n%64))) != 0)
for alln < 64 * longs.length
. Returns:
 a long array containing a littleendian representation of all the bits in this bit set
 Since:
 1.7

flip
public 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

flip
public 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 fliptoIndex
 index after the last bit to flip Throws:
IndexOutOfBoundsException
 iffromIndex
is negative, ortoIndex
is negative, orfromIndex
is larger thantoIndex
 Since:
 1.4

set
public 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

set
public void set(int bitIndex, boolean value) Sets the bit at the specified index to the specified value. Parameters:
bitIndex
 a bit indexvalue
 a boolean value to set Throws:
IndexOutOfBoundsException
 if the specified index is negative Since:
 1.4

set
public 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 settoIndex
 index after the last bit to be set Throws:
IndexOutOfBoundsException
 iffromIndex
is negative, ortoIndex
is negative, orfromIndex
is larger thantoIndex
 Since:
 1.4

set
public 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 settoIndex
 index after the last bit to be setvalue
 value to set the selected bits to Throws:
IndexOutOfBoundsException
 iffromIndex
is negative, ortoIndex
is negative, orfromIndex
is larger thantoIndex
 Since:
 1.4

clear
public 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

clear
public 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 clearedtoIndex
 index after the last bit to be cleared Throws:
IndexOutOfBoundsException
 iffromIndex
is negative, ortoIndex
is negative, orfromIndex
is larger thantoIndex
 Since:
 1.4

clear
public void clear()Sets all of the bits in this BitSet tofalse
. Since:
 1.4

get
public boolean get(int bitIndex) Returns the value of the bit with the specified index. The value istrue
if the bit with the indexbitIndex
is 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

get
Returns a newBitSet
composed of bits from thisBitSet
fromfromIndex
(inclusive) totoIndex
(exclusive). Parameters:
fromIndex
 index of the first bit to includetoIndex
 index after the last bit to include Returns:
 a new
BitSet
from a range of thisBitSet
 Throws:
IndexOutOfBoundsException
 iffromIndex
is negative, ortoIndex
is negative, orfromIndex
is larger thantoIndex
 Since:
 1.4

nextSetBit
public int nextSetBit(int fromIndex) Returns the index of the first bit that is set totrue
that occurs on or after the specified starting index. If no such bit exists then1
is returned.To iterate over the
true
bits 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
1
if there is no such bit  Throws:
IndexOutOfBoundsException
 if the specified index is negative Since:
 1.4

nextClearBit
public int nextClearBit(int fromIndex) Returns the index of the first bit that is set tofalse
that 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

previousSetBit
public int previousSetBit(int fromIndex) Returns the index of the nearest bit that is set totrue
that occurs on or before the specified starting index. If no such bit exists, or if1
is given as the starting index, then1
is returned.To iterate over the
true
bits in aBitSet
, use the following loop:for (int i = bs.length(); (i = bs.previousSetBit(i1)) >= 0; ) { // operate on index i here }
 Parameters:
fromIndex
 the index to start checking from (inclusive) Returns:
 the index of the previous set bit, or
1
if there is no such bit  Throws:
IndexOutOfBoundsException
 if the specified index is less than1
 Since:
 1.7

previousClearBit
public int previousClearBit(int fromIndex) Returns the index of the nearest bit that is set tofalse
that occurs on or before the specified starting index. If no such bit exists, or if1
is given as the starting index, then1
is returned. Parameters:
fromIndex
 the index to start checking from (inclusive) Returns:
 the index of the previous clear bit, or
1
if there is no such bit  Throws:
IndexOutOfBoundsException
 if the specified index is less than1
 Since:
 1.7

length
public int length()Returns the "logical size" of thisBitSet
: the index of the highest set bit in theBitSet
plus one. Returns zero if theBitSet
contains no set bits. Returns:
 the logical size of this
BitSet
 Since:
 1.2

isEmpty
public boolean isEmpty()Returns true if thisBitSet
contains no bits that are set totrue
. Returns:
 boolean indicating whether this
BitSet
is empty  Since:
 1.4

intersects
Returns true if the specifiedBitSet
has any bits set totrue
that are also set totrue
in thisBitSet
. Parameters:
set
BitSet
to intersect with Returns:
 boolean indicating whether this
BitSet
intersects the specifiedBitSet
 Since:
 1.4

cardinality
public int cardinality()Returns the number of bits set totrue
in thisBitSet
. Returns:
 the number of bits set to
true
in thisBitSet
 Since:
 1.4

and
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 valuetrue
if and only if it both initially had the valuetrue
and the corresponding bit in the bit set argument also had the valuetrue
. Parameters:
set
 a bit set

or
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 valuetrue
if and only if it either already had the valuetrue
or the corresponding bit in the bit set argument has the valuetrue
. Parameters:
set
 a bit set

xor
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 valuetrue
if 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

andNot
Clears all of the bits in thisBitSet
whose corresponding bit is set in the specifiedBitSet
. Parameters:
set
 theBitSet
with which to mask thisBitSet
 Since:
 1.2

hashCode
public 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:
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); }

size
public int size()Returns the number of bits of space actually in use by thisBitSet
to represent bit values. The maximum element in the set is the size  1st element. Returns:
 the number of bits currently in this bit set

equals
Compares this bit set against the specified object. The result istrue
if and only if the argument is notnull
and is aBitSet
object that has exactly the same set of bits set totrue
as this bit set. That is, for every nonnegativeint
indexk
,((BitSet)obj).get(k) == this.get(k)
must be true. The current sizes of the two bit sets are not compared. 
clone

toString
Returns a string representation of this bit set. For every index for which thisBitSet
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();
NowdrPepper.toString()
returns "{}
".drPepper.set(2);
NowdrPepper.toString()
returns "{2}
".drPepper.set(4); drPepper.set(10);
NowdrPepper.toString()
returns "{2, 4, 10}
". 
stream
Returns a stream of indices for which thisBitSet
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 thecardinality()
method.The stream binds to this bit set when the terminal stream operation commences (specifically, the spliterator for the stream is latebinding). 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
