Class BS
- All Implemented Interfaces:
Cloneable
,JSONEncodable
- Direct Known Subclasses:
BondSet
- Since:
- JDK1.0
- Author:
- Bob Hanson hansonr@stolaf.edu
Additions by Bob Hanson to allow for JavaScript mix of int/long Note
that Firefox (Sept 2012) does not really treat "Int32Array" as such,
because any element can be pushed into being a 64-bit number, which
really isn't because the last 8 bits are not usable.
This class implements a vector of bits that grows as needed. Each
component of the bit set has a
boolean
value. The bits of aBitSet
are indexed by nonnegative integers. Individual indexed bits can be examined, set, or cleared. OneBitSet
may be used to modify the contents of anotherBitSet
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 aNullPointerException
.A
BitSet
is not safe for multithreaded use without external synchronization., Arthur van Hoff, Michael McCloskey, Martin Buchholz
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionvoid
Performs a logical AND of this target bit set with the argument bit set.void
Clears all of the bits in thisBitSet
whose corresponding bit is set in the specifiedBitSet
.int
Returns the number of bits set totrue
in thisBitSet
.int
cardinalityN
(int max) void
clear
(int bitIndex) Sets the bit specified by the index tofalse
.void
clearAll()
Sets all of the bits in this BitSet tofalse
.void
clearBits
(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex
(inclusive) to the specifiedtoIndex
(exclusive) tofalse
.clone()
Cloning thisBitSet
produces a newBitSet
that is equal to it.static BS
fast copyboolean
Compares this object against the specified object.static String
boolean
get
(int bitIndex) Returns the value of the bit with the specified index.int
hashCode()
Returns a hash code value for this bit set.boolean
intersects
(BS set) Returns true if the specifiedBitSet
has any bits set totrue
that are also set totrue
in thisBitSet
.boolean
isEmpty()
Returns true if thisBitSet
contains no bits that are set totrue
.int
length()
Returns the "logical size" of thisBitSet
: the index of the highest set bit in theBitSet
plus one.static BS
newN
(int nbits) Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range0
throughnbits-1
.int
nextClearBit
(int fromIndex) Returns the index of the first bit that is set tofalse
that occurs on or after the specified starting index.int
nextSetBit
(int fromIndex) Returns the index of the first bit that is set totrue
that occurs on or after the specified starting index.void
Performs a logical OR of this bit set with the bit set argument.void
set
(int bitIndex) Sets the bit at the specified index totrue
.void
setBits
(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex
(inclusive) to the specifiedtoIndex
(exclusive) totrue
.void
setBitTo
(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 thisBitSet
to represent bit values.toJSON()
toString()
Returns a string representation of this bit set.static BS
void
Performs a logical XOR of this bit set with the bit set argument.
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Constructor Details
-
BS
public BS()Creates a new bit set. All bits are initiallyfalse
.
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-
Method Details
-
newN
Creates a bit set whose initial size is large enough to explicitly represent bits with indices in the range0
throughnbits-1
. All bits are initiallyfalse
.- Parameters:
nbits
- the initial size of the bit set- Returns:
- bs
- Throws:
NegativeArraySizeException
- if the specified initial size is negative
-
set
public void set(int bitIndex) Sets the bit at the specified index totrue
.- Parameters:
bitIndex
- a bit index- Throws:
IndexOutOfBoundsException
- if the specified index is negative- Since:
- JDK1.0
-
setBitTo
public void setBitTo(int bitIndex, boolean value) Sets the bit at the specified index to the specified value.- Parameters:
bitIndex
- a bit indexvalue
- a boolean value to set- Throws:
IndexOutOfBoundsException
- if the specified index is negative- Since:
- 1.4
-
setBits
public void setBits(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex
(inclusive) to the specifiedtoIndex
(exclusive) totrue
.- Parameters:
fromIndex
- index of the first bit to be settoIndex
- index after the last bit to be set- 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 tofalse
.- Parameters:
bitIndex
- the index of the bit to be cleared- Throws:
IndexOutOfBoundsException
- if the specified index is negative- Since:
- JDK1.0
-
clearBits
public void clearBits(int fromIndex, int toIndex) Sets the bits from the specifiedfromIndex
(inclusive) to the specifiedtoIndex
(exclusive) tofalse
.- Parameters:
fromIndex
- index of the first bit to be clearedtoIndex
- index after the last bit to be cleared- Throws:
IndexOutOfBoundsException
- iffromIndex
is negative, ortoIndex
is negative, orfromIndex
is larger thantoIndex
- Since:
- 1.4
-
clearAll
public void clearAll()Sets all of the bits in this BitSet tofalse
.- Since:
- 1.4
-
get
public boolean get(int bitIndex) Returns the value of the bit with the specified index. The value istrue
if the bit with the indexbitIndex
is currently set in thisBitSet
; otherwise, the result isfalse
.- Parameters:
bitIndex
- the bit index- Returns:
- the value of the bit with the specified index
- Throws:
IndexOutOfBoundsException
- if the specified index is negative
-
nextSetBit
public int nextSetBit(int fromIndex) Returns the index of the first bit that is set totrue
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 aBitSet
, use the following loop: -
nextClearBit
public int nextClearBit(int fromIndex) Returns the index of the first bit that is set tofalse
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
-
length
public int length()Returns the "logical size" of thisBitSet
: the index of the highest set bit in theBitSet
plus one. Returns zero if theBitSet
contains no set bits.- Returns:
- the logical size of this
BitSet
- Since:
- 1.2
-
isEmpty
public boolean isEmpty()Returns true if thisBitSet
contains no bits that are set totrue
.- Returns:
- boolean indicating whether this
BitSet
is empty - Since:
- 1.4
-
intersects
Returns true if the specifiedBitSet
has any bits set totrue
that are also set totrue
in thisBitSet
.- 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 totrue
in thisBitSet
.- Returns:
- the number of bits set to
true
in thisBitSet
- Since:
- 1.4
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and
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 valuetrue
if and only if it both initially had the valuetrue
and the corresponding bit in the bit set argument also had the valuetrue
.- Parameters:
set
- a bit set
-
or
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 valuetrue
if and only if it either already had the valuetrue
or the corresponding bit in the bit set argument has the valuetrue
.- Parameters:
set
- a bit set
-
xor
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 valuetrue
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
- The bit initially has the value
-
andNot
Clears all of the bits in thisBitSet
whose corresponding bit is set in the specifiedBitSet
.- Parameters:
set
- theBitSet
with which to mask thisBitSet
- Since:
- 1.2
-
hashCode
public int hashCode()Returns a hash code value for this bit set. The hash code depends only on which bits have been set within thisBitSet
. The algorithm used to compute it may be described as follows.Suppose the bits in the
BitSet
were to be stored in an array oflong
integers called, say,words
, in such a manner that bitk
is set in theBitSet
(for nonnegative values ofk
) if and only if the expression((k >> 6) < words.length) && ((words[k >> 6] & (1 << (bit & 0x3F))) != 0)
is true. Then the following definition of thehashCode
method would be a correct implementation of the actual algorithm:public int hashCode() { long h = 1234; for (int i = words.length; --i >= 0;) { h ˆ= words[i] * (i + 1); } return (int) ((h >> 32) ˆ h); }
Note that the hash code values change if the set of bits is altered.Overrides the
hashCode
method ofObject
. -
size
public int size()Returns the number of bits of space actually in use by thisBitSet
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
Compares this object against the specified object. The result istrue
if and only if the argument is notnull
and is aBitset
object that has exactly the same set of bits set totrue
as this bit set. That is, for every nonnegativeint
indexk
,((BitSet) obj).get(k) == this.get(k)
must be true. The current sizes of the two bit sets are not compared. -
clone
Cloning thisBitSet
produces a newBitSet
that is equal to it. The clone of the bit set is another bit set that has exactly the same bits set totrue
as this bit set. -
toString
Returns a string representation of this bit set. For every index for which thisBitSet
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();
NowdrPepper.toString()
returns "{}".drPepper.set(2);
NowdrPepper.toString()
returns "{2}".drPepper.set(4); drPepper.set(10);
NowdrPepper.toString()
returns "{2, 4, 10}". -
copy
fast copy- Parameters:
bitsetToCopy
-- Returns:
- bs
-
cardinalityN
public int cardinalityN(int max) - Parameters:
max
-- Returns:
- n bits below max
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toJSON
- Specified by:
toJSON
in interfaceJSONEncodable
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escape
-
unescape
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