Class BitSet
 java.lang.Object

 java.util.BitSet
 All Implemented Interfaces:

Serializable
,Cloneable
public class BitSet extends Object implements Cloneable, Serializable
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.
 Since:
 1.0
 See Also:
 Serialized Form
Constructor Summary
Constructor  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 
Method Summary
Modifier and Type  Method  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 
int  cardinality()  Returns the number of bits set to 
void  clear()  Sets all of the bits in this BitSet to 
void  clear(int bitIndex)  Sets the bit specified by the index to 
void  clear(int fromIndex,
int toIndex)  Sets the bits from the specified 
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 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. 
void  set(int fromIndex,
int toIndex)  Sets the bits from the specified 
void  set(int fromIndex,
int toIndex,
boolean value)  Sets the bits from the specified 
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(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  xor(BitSet set)  Performs a logical XOR of this bit set with the bit set argument. 
Methods declared in class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait
Constructor Detail
BitSet
public BitSet()
Creates a new bit set. All bits are initially false
.
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
 the initial size of the bit set  Throws:

NegativeArraySizeException
 if the specified initial size is negative
Method Detail
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
 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
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
 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
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
 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
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
 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();
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:
 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();
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:
 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 specified fromIndex
(inclusive) to the specified toIndex
(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
 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 to true
.
 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 index 
value
 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 specified fromIndex
(inclusive) to the specified toIndex
(exclusive) to true
.
 Parameters:

fromIndex
 index of the first bit to be set 
toIndex
 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 specified fromIndex
(inclusive) to the specified toIndex
(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
 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 to false
.
 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 specified fromIndex
(inclusive) to the specified toIndex
(exclusive) to false
.
 Parameters:

fromIndex
 index of the first bit to be cleared 
toIndex
 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 to false
.
 Since:
 1.4
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
 the bit index  Returns:
 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
 index of the first bit to include 
toIndex
 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 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
 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 to false
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 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
 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 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
 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 this BitSet
: the index of the highest set bit in the BitSet
plus one. Returns zero if the BitSet
contains no set bits.
 Returns:
 the logical size of this
BitSet
 Since:
 1.2
isEmpty
public boolean isEmpty()
Returns true if this BitSet
contains no bits that are set to true
.
 Returns:
 boolean indicating whether this
BitSet
is empty  Since:
 1.4
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
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 to true
in this BitSet
.
 Returns:
 the number of bits set to
true
in thisBitSet
 Since:
 1.4
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
 a bit set
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
 a bit set
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
 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
 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 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.
 Overrides:

hashCode
in classObject
 Returns:
 the hash code value for this bit set
 See Also:

Object.equals(java.lang.Object)
,System.identityHashCode(java.lang.Object)
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:
 the number of bits currently in this bit set
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.
 Overrides:

equals
in classObject
 Parameters:

obj
 the object to compare with  Returns:

true
if the objects are the same;false
otherwise  See Also:
size()
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.
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}
".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 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