BitSet
public
class
BitSet
extends Object
implements
Cloneable,
Serializable
java.lang.Object  
↳  java.util.BitSet 
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.
Summary
Public constructors  

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 
Public methods  

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 
int

cardinality()
Returns the number of bits set to 
void

clear(int fromIndex, int toIndex)
Sets the bits from the specified 
void

clear(int bitIndex)
Sets the bit specified by the index to 
void

clear()
Sets all of the bits in this BitSet to 
Object

clone()
Cloning this 
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 
boolean

get(int bitIndex)
Returns the value of the bit with the specified index. 
BitSet

get(int fromIndex, int toIndex)
Returns a new 
int

hashCode()
Returns the hash code value for this bit set. 
boolean

intersects(BitSet set)
Returns true if the specified 
boolean

isEmpty()
Returns true if this 
int

length()
Returns the "logical size" of this 
int

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

nextSetBit(int fromIndex)
Returns the index of the first bit that is set to 
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 
int

previousSetBit(int fromIndex)
Returns the index of the nearest bit that is set to 
void

set(int fromIndex, int toIndex, boolean value)
Sets the bits from the specified 
void

set(int fromIndex, int toIndex)
Sets the bits from the specified 
void

set(int bitIndex)
Sets the bit at the specified index to 
void

set(int bitIndex, boolean value)
Sets the bit at the specified index to the specified value. 
int

size()
Returns the number of bits of space actually in use by this

IntStream

stream()
Returns a stream of indices for which this 
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(long[] longs)
Returns a new bit set containing all the bits in the given long array. 
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(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. 
Inherited methods  

Public constructors
BitSet
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
nbits1
. All bits are initially false
.
Parameters  

nbits 
int : the initial size of the bit set 
Throws  

NegativeArraySizeException 
if the specified initial size is negative 
Public methods
and
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
.
Parameters  

set 
BitSet : a bit set

andNot
public void andNot (BitSet set)
Clears all of the bits in this BitSet
whose corresponding
bit is set in the specified BitSet
.
Parameters  

set 
BitSet : the BitSet with which to mask this
BitSet 
cardinality
public int cardinality ()
Returns the number of bits set to true
in this BitSet
.
Returns  

int 
the number of bits set to true in this BitSet 
clear
public void clear (int fromIndex, int toIndex)
Sets the bits from the specified fromIndex
(inclusive) to the
specified toIndex
(exclusive) to false
.
Parameters  

fromIndex 
int : index of the first bit to be cleared 
toIndex 
int : index after the last bit to be cleared 
Throws  

IndexOutOfBoundsException 
if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex 
clear
public void clear (int bitIndex)
Sets the bit specified by the index to false
.
Parameters  

bitIndex 
int : the index of the bit to be cleared 
Throws  

IndexOutOfBoundsException 
if the specified index is negative 
clone
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.
Returns  

Object 
a clone of this bit set 
See also:
equals
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.
Parameters  

obj 
Object : the object to compare with 
Returns  

boolean 
true if the objects are the same;
false otherwise 
See also:
flip
public void flip (int bitIndex)
Sets the bit at the specified index to the complement of its current value.
Parameters  

bitIndex 
int : the index of the bit to flip 
Throws  

IndexOutOfBoundsException 
if the specified index is negative 
flip
public 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.
Parameters  

fromIndex 
int : index of the first bit to flip 
toIndex 
int : index after the last bit to flip 
Throws  

IndexOutOfBoundsException 
if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex 
get
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
.
Parameters  

bitIndex 
int : the bit index 
Returns  

boolean 
the value of the bit with the specified index 
Throws  

IndexOutOfBoundsException 
if the specified index is negative 
get
public BitSet get (int fromIndex, int toIndex)
Returns a new BitSet
composed of bits from this BitSet
from fromIndex
(inclusive) to toIndex
(exclusive).
Parameters  

fromIndex 
int : index of the first bit to include 
toIndex 
int : index after the last bit to include 
Returns  

BitSet 
a new BitSet from a range of this BitSet 
Throws  

IndexOutOfBoundsException 
if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex 
hashCode
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.
Returns  

int 
the hash code value for this bit set 
intersects
public 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
.
Parameters  

set 
BitSet : BitSet to intersect with 
Returns  

boolean 
boolean indicating whether this BitSet intersects
the specified BitSet 
isEmpty
public boolean isEmpty ()
Returns true if this BitSet
contains no bits that are set
to true
.
Returns  

boolean 
boolean indicating whether this BitSet is empty 
length
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.
Returns  

int 
the logical size of this BitSet 
nextClearBit
public 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.
Parameters  

fromIndex 
int : the index to start checking from (inclusive) 
Returns  

int 
the index of the next clear bit 
Throws  

IndexOutOfBoundsException 
if the specified index is negative 
nextSetBit
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
}
}
Parameters  

fromIndex 
int : the index to start checking from (inclusive) 
Returns  

int 
the index of the next set bit, or 1 if there
is no such bit 
Throws  

IndexOutOfBoundsException 
if the specified index is negative 
or
public 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
.
Parameters  

set 
BitSet : a bit set

previousClearBit
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.
Parameters  

fromIndex 
int : the index to start checking from (inclusive) 
Returns  

int 
the index of the previous clear bit, or 1 if there
is no such bit 
Throws  

IndexOutOfBoundsException 
if the specified index is less
than 1 
previousSetBit
public 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(i1)) >= 0; ) {
// operate on index i here
}
Parameters  

fromIndex 
int : the index to start checking from (inclusive) 
Returns  

int 
the index of the previous set bit, or 1 if there
is no such bit 
Throws  

IndexOutOfBoundsException 
if the specified index is less
than 1 
set
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.
Parameters  

fromIndex 
int : index of the first bit to be set 
toIndex 
int : index after the last bit to be set 
value 
boolean : value to set the selected bits to 
Throws  

IndexOutOfBoundsException 
if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex 
set
public void set (int fromIndex, int toIndex)
Sets the bits from the specified fromIndex
(inclusive) to the
specified toIndex
(exclusive) to true
.
Parameters  

fromIndex 
int : index of the first bit to be set 
toIndex 
int : index after the last bit to be set 
Throws  

IndexOutOfBoundsException 
if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex 
set
public void set (int bitIndex)
Sets the bit at the specified index to true
.
Parameters  

bitIndex 
int : a bit index 
Throws  

IndexOutOfBoundsException 
if the specified index is negative 
set
public void set (int bitIndex, boolean value)
Sets the bit at the specified index to the specified value.
Parameters  

bitIndex 
int : a bit index 
value 
boolean : a boolean value to set 
Throws  

IndexOutOfBoundsException 
if the specified index is negative 
size
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.
Returns  

int 
the number of bits currently in this bit set 
stream
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.
Returns  

IntStream 
a stream of integers representing set indices 
toByteArray
public 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
.
Returns  

byte[] 
a byte array containing a littleendian representation of all the bits in this bit set 
toLongArray
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
.
Returns  

long[] 
a long array containing a littleendian representation of all the bits in this bit set 
toString
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}
".
Returns  

String 
a string representation of this bit set 
valueOf
public 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))
.
Parameters  

longs 
long : 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  

BitSet 
a BitSet containing all the bits in the long array 
valueOf
public 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))
.
Parameters  

bytes 
byte : 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  

BitSet 
a BitSet containing all the bits in the byte array 
valueOf
public 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.
Parameters  

bb 
ByteBuffer : 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  

BitSet 
a BitSet containing all the bits in the buffer in the
specified range 
valueOf
public 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.
Parameters  

lb 
LongBuffer : 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  

BitSet 
a BitSet containing all the bits in the buffer in the
specified range 
xor
public 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:
 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 
BitSet : a bit set

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