Added in API level 1

Summary: Ctors | Methods | Inherited Methods

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 Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. final Class<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public constructors

BitSet

Added in API level 1

public BitSet ()

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

BitSet

Added in API level 1

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 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

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

clear

Added in API level 1

public void clear ()

Sets all of the bits in this BitSet to false.

clone

Added in API level 1

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:

• size()

equals

Added in API level 1

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:

• size()

flip

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 19

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

Added in API level 19

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(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

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 1

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

Added in API level 24

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 late-binding). If the bit set is modified during that operation then the result is undefined.

Returns
IntStream	a stream of integers representing set indices

toByteArray

Added in API level 19

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 little-endian representation of all the bits in this bit set

toLongArray

Added in API level 19

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 little-endian representation of all the bits in this bit set

toString

Added in API level 1

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

Added in API level 19

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 little-endian 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

Added in API level 19

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 little-endian 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

Added in API level 19

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 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	a BitSet containing all the bits in the buffer in the specified range

valueOf

Added in API level 19

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 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	a BitSet containing all the bits in the buffer in the specified range

xor

Added in API level 1

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 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