
Java^{TM} 2 Platform Std. Ed. v1.3 

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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.
Constructor Summary  
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
nbits1 . 
Method Summary  
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 . 
void 
clear(int bitIndex)
Sets the bit specified by the index 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. 
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. 
int 
length()
Returns the "logical size" of this BitSet : the index of
the highest set bit in the BitSet plus one. 
void 
or(BitSet set)
Performs a logical OR of this bit set with the bit set argument. 
void 
set(int bitIndex)
Sets the bit specified by the index to true . 
int 
size()
Returns the number of bits of space actually in use by this BitSet to represent bit values. 
String 
toString()
Returns a string representation of this bit set. 
void 
xor(BitSet set)
Performs a logical XOR of this bit set with the bit set argument. 
Methods inherited from class java.lang.Object 
finalize, getClass, notify, notifyAll, wait, wait, wait 
Constructor Detail 
public BitSet()
false
.public BitSet(int nbits)
0
through
nbits1
. All bits are initially false
.nbits
 the initial size of the bit set.NegativeArraySizeException
 if the specified initial size
is negative.Method Detail 
public 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 void set(int bitIndex)
true
.bitIndex
 a bit index.IndexOutOfBoundsException
 if the specified index is negative.public void clear(int bitIndex)
false
.bitIndex
 the index of the bit to be cleared.IndexOutOfBoundsException
 if the specified index is negative.public void andNot(BitSet set)
BitSet
whose corresponding
bit is set in the specified BitSet
.set
 the BitSet
with which to mask this
BitSet
.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 index.IndexOutOfBoundsException
 if the specified index is negative.public void and(BitSet 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 set.public void or(BitSet 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 set.public void xor(BitSet 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 set.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,
bits
, 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) < bits.length) && ((bits[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 synchronized int hashCode() { long h = 1234; for (int i = bits.length; i >= 0; ) { h ^= bits[i] * (i + 1); } return (int)((h >> 32) ^ h); }Note that the hash code values change if the set of bits is altered.
Overrides the hashCode
method of Object
.
hashCode
in class Object
public int size()
BitSet
to represent bit values.
The maximum element in the set is the size  1st element.public boolean equals(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.
Overrides the equals
method of Object
.
equals
in class Object
obj
 the object to compare with.true
if the objects are the same;
false
otherwise.size()
public 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 and the same
current size.
Overrides the clone
method of Object
.
clone
in class Object
size()
public String toString()
BitSet
contains a bit in the set
state, the decimal representation of that index is included in
the result. Such indeces aer listed in order from lowest to
highest, separated by ",$nbsp;" (a comma and a space) and
surrounded by braces, resulting in the usual mathematical
notation for a set of integers.
Overrides the toString
method of Object
.
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}
".toString
in class Object

Java^{TM} 2 Platform Std. Ed. v1.3 

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