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

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 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 andNot(BitSet set)
BitSet
whose corresponding bit is set in the specified BitSet
.set
 the BitSet
with which to mask this BitSet
public int cardinality()
true
in this BitSet
.true
in this BitSet
public void clear()
false
.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 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 boolean equals(@Nullable 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 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 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 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 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 boolean isEmpty()
BitSet
contains no bits that are set to true
.BitSet
is emptypublic 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 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 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 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 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 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 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 int size()
BitSet
to represent bit values. The maximum
element in the set is the size  1st element.public 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 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
".public 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 setBitSet
containing all the bits in the byte arraypublic 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 setBitSet
containing all the bits in the long arraypublic 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 set