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Added in API level 1

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 0 through nbits-1.

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 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(int fromIndex, int toIndex)

Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) to false.

void clear(int bitIndex)

Sets the bit specified by the index to false.

void clear()

Sets all of the bits in this BitSet 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 fromIndex, int toIndex, boolean value)

Sets the bits from the specified fromIndex (inclusive) to the specified toIndex (exclusive) 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 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.

int size()

Returns the number of bits of space actually in use by this BitSet to represent bit values.

IntStream stream()

Returns a stream of indices for which this BitSet contains a bit in the set state.

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

From class java.lang.Object

Public constructors

BitSet

Added in API level 1
BitSet ()

Creates a new bit set. All bits are initially false.

BitSet

Added in API level 1
BitSet (int nbits)

Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range 0 through nbits-1. 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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

clear

Added in API level 1
void clear ()

Sets all of the bits in this BitSet to false.

clone

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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
 }

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

Added in API level 1
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

Added in API level 19
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

Added in API level 19
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(i-1)) >= 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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 1
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

Added in API level 24
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

Added in API level 19
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 little-endian representation of all the bits in this bit set

toLongArray

Added in API level 19
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 little-endian representation of all the bits in this bit set

toString

Added in API level 1
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

Added in API level 19
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 little-endian representation of a sequence of bits to be used as the initial bits of the new bit set
Returns
BitSet

valueOf

Added in API level 19
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 little-endian representation of a sequence of bits to be used as the initial bits of the new bit set
Returns
BitSet

valueOf

Added in API level 19
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 little-endian 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

valueOf

Added in API level 19
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 little-endian 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

xor

Added in API level 1
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 value false.
  • The bit initially has the value false, and the corresponding bit in the argument has the value true.

Parameters
set BitSet: a bit set
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