public class BS
extends java.lang.Object
implements java.lang.Cloneable, javajs.api.JSONEncodable
boolean
value. The bits of a
BitSet
are indexed by nonnegative integers. Individual
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., Arthur van Hoff, Michael McCloskey, Martin Buchholz
Modifier and Type | Field and 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.
|
Constructor and Description |
---|
BS()
Creates a new bit set.
|
Modifier and Type | Method and 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 this
BitSet whose corresponding bit is
set in the specified BitSet . |
int |
cardinality()
Returns the number of bits set to
true in this BitSet . |
int |
cardinalityN(int max) |
void |
clear(int bitIndex)
Sets the bit specified by the index to
false . |
void |
clearAll()
Sets all of the bits in this BitSet to
false . |
void |
clearBits(int fromIndex,
int toIndex)
Sets the bits from the specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to false . |
java.lang.Object |
clone()
Cloning this
BitSet produces a new BitSet 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 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. |
static BS |
newN(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 . |
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(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 to
true . |
void |
setBits(int fromIndex,
int toIndex)
Sets the bits from the specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to true . |
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 this
BitSet
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.
|
private static final int ADDRESS_BITS_PER_WORD
private static final int BITS_PER_WORD
private static final long WORD_MASK
private long[] words
private transient int wordsInUse
private transient boolean sizeIsSticky
private static final long[] emptyBitmap
private static int wordIndex(int bitIndex)
bitIndex
- public static BS newN(int nbits)
0
through nbits-1
.
All bits are initially false
.nbits
- the initial size of the bit setjava.lang.NegativeArraySizeException
- if the specified initial size is negativeprivate void recalculateWordsInUse()
private void init(int nbits)
private void initWords(int nbits)
private void ensureCapacity(int wordsRequired)
wordsRequired
- the minimum acceptable number of words.private void expandTo(int wordIndex)
wordIndex
- the index to be accommodated.public void set(int bitIndex)
true
.bitIndex
- a bit indexjava.lang.IndexOutOfBoundsException
- if the specified index is negativepublic void setBitTo(int bitIndex, boolean value)
bitIndex
- a bit indexvalue
- a boolean value to setjava.lang.IndexOutOfBoundsException
- if the specified index is negativepublic void setBits(int fromIndex, int toIndex)
fromIndex
(inclusive) to the
specified toIndex
(exclusive) to true
.fromIndex
- index of the first bit to be settoIndex
- index after the last bit to be setjava.lang.IndexOutOfBoundsException
- if fromIndex
is negative, or toIndex
is negative,
or fromIndex
is larger than toIndex
public void clear(int bitIndex)
false
.bitIndex
- the index of the bit to be clearedjava.lang.IndexOutOfBoundsException
- if the specified index is negativepublic void clearBits(int fromIndex, int toIndex)
fromIndex
(inclusive) to the
specified toIndex
(exclusive) to false
.fromIndex
- index of the first bit to be clearedtoIndex
- index after the last bit to be clearedjava.lang.IndexOutOfBoundsException
- if fromIndex
is negative, or toIndex
is negative,
or fromIndex
is larger than toIndex
public void clearAll()
false
.public boolean get(int bitIndex)
true
if the bit with the index bitIndex
is currently set in this
BitSet
; otherwise, the result is false
.bitIndex
- the bit indexjava.lang.IndexOutOfBoundsException
- if the specified index is negativepublic int nextSetBit(int fromIndex)
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:
fromIndex
- the index to start checking from (inclusive)-1
if there is no such
bitjava.lang.IndexOutOfBoundsException
- if the specified index is negativepublic int nextClearBit(int fromIndex)
false
that occurs
on or after the specified starting index.fromIndex
- the index to start checking from (inclusive)java.lang.IndexOutOfBoundsException
- if the specified index is negativepublic int length()
BitSet
: the index of the highest
set bit in the BitSet
plus one. Returns zero if the BitSet
contains no set bits.BitSet
public boolean isEmpty()
BitSet
contains no bits that are set to
true
.BitSet
is emptypublic boolean intersects(BS set)
BitSet
has any bits set to true
that are also set to true
in this BitSet
.set
- BitSet
to intersect withBitSet
intersects the
specified BitSet
public int cardinality()
true
in this BitSet
.true
in this BitSet
public void and(BS set)
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
.set
- a bit setpublic void or(BS set)
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
.set
- a bit setpublic void xor(BS set)
true
if
and only if one of the following statements holds:
true
, and the corresponding bit
in the argument has the value false
.
false
, and the corresponding
bit in the argument has the value true
.
set
- a bit setpublic void andNot(BS set)
BitSet
whose corresponding bit is
set in the specified BitSet
.set
- the BitSet
with which to mask this BitSet
public int hashCode()
BitSet
. The algorithm
used to compute it may be described as follows.
Suppose the bits in the BitSet
were to be stored in an array
of long
integers called, say, words
, in such a
manner that bit k
is set in the BitSet
(for
nonnegative values of k
) if and only if the expression
((k >> 6) < words.length) && ((words[k >> 6] & (1L << (bit & 0x3F))) != 0)is true. Then the following definition of the
hashCode
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 of Object
.
hashCode
in class java.lang.Object
public int size()
BitSet
to represent bit values. The maximum element in the set is the size - 1st
element.public boolean equals(java.lang.Object obj)
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.
equals
in class java.lang.Object
obj
- the object to compare withtrue
if the objects are the same; false
otherwisesize()
public java.lang.Object clone()
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.clone
in class java.lang.Object
size()
private void setLength(int n)
public java.lang.String toString()
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 empty braces.
drPepper.set(2);Now
drPepper.toString()
returns "{2}".
drPepper.set(4); drPepper.set(10);Now
drPepper.toString()
returns "{2, 4, 10}".toString
in class java.lang.Object
public int cardinalityN(int max)
max
- public java.lang.String toJSON()
toJSON
in interface javajs.api.JSONEncodable
public static BS unescape(java.lang.String str)
str
- public static java.lang.String escape(BS bs, char chOpen, char chClose)