public class BitSet extends Object implements Cloneable, Serializable
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.
Constructor and Description 

BitSet()
Creates a new bit set.

BitSet(int nbits)
Creates a bit set whose initial size is large enough to explicitly
represent bits with indices in the range
0 through
nbits1 . 
Modifier and Type  Method and Description 

void 
and(BitSet set)
Performs a logical AND of this target bit set with the
argument bit set.

void 
andNot(BitSet set)
Clears all of the bits in this
BitSet whose corresponding
bit is set in the specified BitSet . 
int 
cardinality()
Returns the number of bits set to
true in this BitSet . 
void 
clear()
Sets all of the bits in this BitSet to
false . 
void 
clear(int bitIndex)
Sets the bit specified by the index to
false . 
void 
clear(int fromIndex,
int toIndex)
Sets the bits from the specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to false . 
Object 
clone()
Cloning this
BitSet produces a new BitSet
that is equal to it. 
boolean 
equals(Object obj)
Compares this object 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 specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to the complement of its current
value. 
boolean 
get(int bitIndex)
Returns the value of the bit with the specified index.

BitSet 
get(int fromIndex,
int toIndex)
Returns a new
BitSet composed of bits from this BitSet
from fromIndex (inclusive) to toIndex (exclusive). 
int 
hashCode()
Returns the hash code value for this bit set.

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 . 
boolean 
isEmpty()
Returns true if this
BitSet contains no bits that are set
to true . 
int 
length()
Returns the "logical size" of this
BitSet : the index of
the highest set bit in the BitSet plus one. 
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. 
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. 
void 
or(BitSet set)
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 to
false
that occurs on or before the specified starting index. 
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. 
void 
set(int bitIndex)
Sets the bit at the specified index to
true . 
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 specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to true . 
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. 
int 
size()
Returns the number of bits of space actually in use by this
BitSet to represent bit values. 
byte[] 
toByteArray()
Returns a new byte array containing all the bits in this bit set.

long[] 
toLongArray()
Returns a new long array containing all the bits in this bit set.

String 
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(ByteBuffer bb)
Returns a new bit set containing all the bits in the given byte
buffer between its position and limit.

static BitSet 
valueOf(long[] longs)
Returns a new bit set containing all the bits in the given long array.

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 
xor(BitSet set)
Performs a logical XOR of this bit set with the bit set
argument.

public BitSet()
false
.public BitSet(int nbits)
0
through
nbits1
. 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)
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 littleendian representation
of a sequence of bits to be used as the initial bits of the
new bit setpublic static BitSet valueOf(LongBuffer lb)
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 littleendian representation
of a sequence of bits between its position and limit, to be
used as the initial bits of the new bit setpublic static BitSet valueOf(byte[] bytes)
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 littleendian
representation of a sequence of bits to be used as the
initial bits of the new bit setpublic static BitSet valueOf(ByteBuffer bb)
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 littleendian representation
of a sequence of bits between its position and limit, to be
used as the initial bits of the new bit setpublic byte[] toByteArray()
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()
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)
bitIndex
 the index of the bit to flipIndexOutOfBoundsException
 if the specified index is negativepublic void flip(int fromIndex, int toIndex)
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)
true
.bitIndex
 a bit indexIndexOutOfBoundsException
 if the specified index is negativepublic void set(int bitIndex, boolean value)
bitIndex
 a bit indexvalue
 a boolean value to setIndexOutOfBoundsException
 if the specified index is negativepublic void set(int fromIndex, int toIndex)
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)
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)
false
.bitIndex
 the index of the bit to be clearedIndexOutOfBoundsException
 if the specified index is negativepublic void clear(int fromIndex, int toIndex)
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()
false
.public boolean get(int bitIndex)
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)
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)
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
}
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)
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)
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(i1)) >= 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)
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()
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()
BitSet
contains no bits that are set
to true
.BitSet
is emptypublic boolean intersects(BitSet set)
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()
true
in this BitSet
.true
in this BitSet
public void and(BitSet set)
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)
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)
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)
BitSet
whose corresponding
bit is set in the specified BitSet
.set
 the BitSet
with which to mask this
BitSet
public int hashCode()
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()
BitSet
to represent bit values.
The maximum element in the set is the size  1st element.public boolean equals(Object obj)
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.
public Object clone()
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()
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}
". Submit a bug or feature
For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developertargeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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