Class BS
- java.lang.Object
-
- org.jmol.java.BS
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- All Implemented Interfaces:
java.lang.Cloneable
,javajs.api.JSONEncodable
- Direct Known Subclasses:
BondSet
,SmilesRing
public class BS extends java.lang.Object implements java.lang.Cloneable, javajs.api.JSONEncodable
a fast 64-bit BitSet optimized as 32-bit in Java2Script -- about 25 times faster than java.util.BitSet in JavaScript.- Since:
- JDK1.0
- Author:
- Bob Hanson hansonr@stolaf.edu
This class implements a 64-bit 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 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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Field Summary
Fields Modifier and Type Field Description private static int
ADDRESS_BITS_PER_WORD
private static int
BITS_PER_WORD
private static long[]
emptyBitmap
private boolean
sizeIsSticky
Whether the size of "words" is user-specified.private static long
WORD_MASK
private long[]
words
The internal field corresponding to the serialField "bits".private int
wordsInUse
The number of words in the logical size of this BitSet.
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Constructor Summary
Constructors Constructor Description BS()
Creates a new bit set.
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Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description void
and(BS set)
Performs a logical AND of this target bit set with the argument bit set.void
andNot(BS set)
Clears all of the bits in thisBitSet
whose corresponding bit is set in the specifiedBitSet
.int
cardinality()
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
.java.lang.Object
clone()
Cloning thisBitSet
produces a newBitSet
that is equal to it.private void
ensureCapacity(int wordsRequired)
Ensures that the BitSet can hold enough words.boolean
equals(java.lang.Object obj)
Compares this object against the specified object.static java.lang.String
escape(BS bs, char chOpen, char chClose)
private void
expandTo(int wordIndex)
Ensures that the BitSet can accommodate a given wordIndex, temporarily violating the invariants.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.private void
init(int nbits)
private void
initWords(int nbits)
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
or(BS set)
Performs a logical OR of this bit set with the bit set argument.private void
recalculateWordsInUse()
Sets the field wordsInUse to the logical size in words of the bit set.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.private void
setLength(int n)
int
size()
Returns the number of bits of space actually in use by thisBitSet
to represent bit values.java.lang.String
toJSON()
java.lang.String
toString()
Returns a string representation of this bit set.static BS
unescape(java.lang.String str)
({ 1 2 3:5 }) or ({null}) or [{ 1 2 3:5 }]private static int
wordIndex(int bitIndex)
Given a bit index, return word index containing it.void
xor(BS set)
Performs a logical XOR of this bit set with the bit set argument.
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Field Detail
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ADDRESS_BITS_PER_WORD
private static final int ADDRESS_BITS_PER_WORD
- See Also:
- Constant Field Values
-
BITS_PER_WORD
private static final int BITS_PER_WORD
- See Also:
- Constant Field Values
-
WORD_MASK
private static final long WORD_MASK
- See Also:
- Constant Field Values
-
words
private long[] words
The internal field corresponding to the serialField "bits".
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wordsInUse
private transient int wordsInUse
The number of words in the logical size of this BitSet.
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sizeIsSticky
private transient boolean sizeIsSticky
Whether the size of "words" is user-specified. If so, we assume the user knows what he's doing and try harder to preserve it.
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emptyBitmap
private static final long[] emptyBitmap
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Method Detail
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wordIndex
private static int wordIndex(int bitIndex)
Given a bit index, return word index containing it.- Parameters:
bitIndex
-- Returns:
- index
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newN
public 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
. All bits are initiallyfalse
.- Parameters:
nbits
- the initial size of the bit set- Returns:
- bs
- Throws:
java.lang.NegativeArraySizeException
- if the specified initial size is negative
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recalculateWordsInUse
private void recalculateWordsInUse()
Sets the field wordsInUse to the logical size in words of the bit set. WARNING:This method assumes that the number of words actually in use is less than or equal to the current value of wordsInUse!
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init
private void init(int nbits)
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initWords
private void initWords(int nbits)
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ensureCapacity
private void ensureCapacity(int wordsRequired)
Ensures that the BitSet can hold enough words.- Parameters:
wordsRequired
- the minimum acceptable number of words.
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expandTo
private void expandTo(int wordIndex)
Ensures that the BitSet can accommodate a given wordIndex, temporarily violating the invariants. The caller must restore the invariants before returning to the user, possibly using recalculateWordsInUse().- Parameters:
wordIndex
- the index to be accommodated.
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set
public void set(int bitIndex)
Sets the bit at the specified index totrue
.- Parameters:
bitIndex
- a bit index- Throws:
java.lang.IndexOutOfBoundsException
- if the specified index is negative- Since:
- JDK1.0
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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:
java.lang.IndexOutOfBoundsException
- if the specified index is negative- Since:
- 1.4
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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:
java.lang.IndexOutOfBoundsException
- iffromIndex
is negative, ortoIndex
is negative, orfromIndex
is larger thantoIndex
- Since:
- 1.4
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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:
java.lang.IndexOutOfBoundsException
- if the specified index is negative- Since:
- JDK1.0
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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:
java.lang.IndexOutOfBoundsException
- iffromIndex
is negative, ortoIndex
is negative, orfromIndex
is larger thantoIndex
- Since:
- 1.4
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clearAll
public void clearAll()
Sets all of the bits in this BitSet tofalse
.- Since:
- 1.4
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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:
java.lang.IndexOutOfBoundsException
- if the specified index is negative
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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:
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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:
java.lang.IndexOutOfBoundsException
- if the specified index is negative- Since:
- 1.4
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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
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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
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intersects
public boolean intersects(BS set)
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
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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
public void and(BS 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 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
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or
public void or(BS 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 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
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xor
public void xor(BS 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 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
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andNot
public void andNot(BS set)
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
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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] & (1L << (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
.- Overrides:
hashCode
in classjava.lang.Object
- Returns:
- a hash code value for this bit set.
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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
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equals
public boolean equals(java.lang.Object obj)
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.- Overrides:
equals
in classjava.lang.Object
- Parameters:
obj
- the object to compare with- Returns:
true
if the objects are the same;false
otherwise- See Also:
size()
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clone
public java.lang.Object 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.- Overrides:
clone
in classjava.lang.Object
- Returns:
- a clone of this bit set
- See Also:
size()
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setLength
private void setLength(int n)
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toString
public java.lang.String 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 empty braces.drPepper.set(2);
NowdrPepper.toString()
returns "{2}".drPepper.set(4); drPepper.set(10);
NowdrPepper.toString()
returns "({2, 4, 10})".- Overrides:
toString
in classjava.lang.Object
- Returns:
- a string representation of this bit set
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cardinalityN
public int cardinalityN(int max)
- Parameters:
max
-- Returns:
- n bits below max
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toJSON
public java.lang.String toJSON()
- Specified by:
toJSON
in interfacejavajs.api.JSONEncodable
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unescape
public static BS unescape(java.lang.String str)
({ 1 2 3:5 }) or ({null}) or [{ 1 2 3:5 }]- Parameters:
str
-- Returns:
- BS
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escape
public static java.lang.String escape(BS bs, char chOpen, char chClose)
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