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java.util.BitSet
BitSet
object is a set of bits that grows as needed. The bits of a BitSet
are
indexed by nonnegative integers. Each bit can be individually 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.
public final classBitSet
implements Cloneable { publicBitSet
(); publicBitSet
(int nbits); public StringtoString
(); public booleanequals
(Object obj) public inthashCode
(); public Objectclone
(); public booleanget
(int bitIndex); public voidset
(int bitIndex); public voidclear
(int bitIndex); public voidand
(BitSet set); public voidor
(BitSet set); public voidxor
(BitSet set); public intsize
(); }
21.2.1 public
BitSet
()
This constructor initializes a newly created BitSet
so that all bits are clear.
21.2.2 public
BitSet
(int nbits)
This constructor initializes a newly created BitSet
so that all bits are clear.
Enough space is reserved to explicitly represent bits with indices in the range 0
through nbits1
.
21.2.3 public String
toString
()
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.
Overrides the toString
method of Object
(§20.1.2).
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}"
.
21.2.4 public boolean
equals
(Object obj)
The result is true
if and only if the argument is not null
and is a BitSet
object
such that, for every nonnegative int
index k
:
((BitSet)obj).get(k) == this.get(k)Overrides the
equals
method of Object
(§20.1.3).21.2.5 public int
hashCode
()
The hash code depends only on which bits have been set within this 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 value changes if the set of bits is altered.
Overrides the hashCode
method of Object
(§20.1.4).
21.2.6 public Object
clone
()
Cloning this BitSet
produces a new BitSet
that is equal to it.
Overrides the clone
method of Object
(§20.1.5).
21.2.7 public boolean
get
(int bitIndex)
The result is true
if the bit with index bitIndex
is currently set in this BitSet
;
otherwise, the result is false
.
If bitIndex
is negative, an IndexOutOfBoundsException
is thrown.
21.2.8 public void
set
(int bitIndex)
The bit with index bitIndex
in this BitSet
is changed to the "set" (true
) state.
If bitIndex
is negative, an IndexOutOfBoundsException
is thrown.
If bitIndex
is not smaller than the value that would be returned by the size
method (§21.2.13), then the size of this BitSet
is increased to be larger than bitIndex
.
21.2.9 public void
clear
(int bitIndex)
The bit with index bitIndex
in this BitSet
is changed to the "clear" (false
)
state.
If bitIndex
is negative, an IndexOutOfBoundsException
is thrown.
If bitIndex
is not smaller than the value that would be returned by the size
method (§21.2.13), then the size of this BitSet
is increased to be larger than bitIndex
.
21.2.10 public void
and
(BitSet set)
This BitSet
may be modified by clearing some of its bits. For every nonnegative
int
index k
, bit k
of this BitSet
is cleared if bit k
of set
is clear.
21.2.11 public void
or
(BitSet set)
This BitSet
may be modified by setting some of its bits. For every nonnegative
int
index k
, bit k
of this BitSet
is set if bit k
of set
is set.
21.2.12 public void
xor
(BitSet set)
This BitSet
may be modified by inverting some of its bits. For every nonnegative
int
index k
, bit k
of this BitSet
is inverted if bit k
of set
is set.
21.2.13 public int
size
()
This method returns the number of bits of space actually in use by this BitSet
to
represent bit values.
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Java Language Specification (HTML generated by Suzette Pelouch on February 24, 1998)
Copyright © 1996 Sun Microsystems, Inc.
All rights reserved
Please send any comments or corrections to doug.kramer@sun.com