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.
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.
Public Constructors | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Creates a new bit set.
| |||||||||||
Creates a bit set whose initial size is large enough to explicitly
represent bits with indices in the range
0 through
nbits-1 . |
Public Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Performs a logical AND of this target bit set with the
argument bit set.
| |||||||||||
Clears all of the bits in this
BitSet whose corresponding
bit is set in the specified BitSet . | |||||||||||
Returns the number of bits set to
true in this BitSet . | |||||||||||
Sets the bit specified by the index to
false . | |||||||||||
Sets all of the bits in this BitSet to
false . | |||||||||||
Sets the bits from the specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to false . | |||||||||||
Cloning this
BitSet produces a new BitSet
that is equal to it. | |||||||||||
Compares this object against the specified object.
| |||||||||||
Sets the bit at the specified index to the complement of its
current value.
| |||||||||||
Sets each bit from the specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to the complement of its current
value. | |||||||||||
Returns the value of the bit with the specified index.
| |||||||||||
Returns a new
BitSet composed of bits from this BitSet
from fromIndex (inclusive) to toIndex (exclusive). | |||||||||||
Returns a hash code value for this bit set.
| |||||||||||
Returns true if the specified
BitSet has any bits set to
true that are also set to true in this BitSet . | |||||||||||
Returns true if this
BitSet contains no bits that are set
to true . | |||||||||||
Returns the "logical size" of this
BitSet : the index of
the highest set bit in the BitSet plus one. | |||||||||||
Returns the index of the first bit that is set to
false
that occurs on or after the specified starting index. | |||||||||||
Returns the index of the first bit that is set to
true
that occurs on or after the specified starting index. | |||||||||||
Performs a logical OR of this bit set with the bit set
argument.
| |||||||||||
Sets the bit at the specified index to the specified value.
| |||||||||||
Sets the bits from the specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to the specified value. | |||||||||||
Sets the bits from the specified
fromIndex (inclusive) to the
specified toIndex (exclusive) to true . | |||||||||||
Sets the bit at the specified index to
true . | |||||||||||
Returns the number of bits of space actually in use by this
BitSet to represent bit values. | |||||||||||
Returns a string representation of this bit set.
| |||||||||||
Performs a logical XOR of this bit set with the bit set
argument.
|
[Expand]
Inherited Methods | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
From class
java.lang.Object
|
Creates a new bit set. All bits are initially false
.
Creates a bit set whose initial size is large enough to explicitly
represent bits with indices in the range 0
through
nbits-1
. All bits are initially false
.
nbits | the initial size of the bit set |
---|
NegativeArraySizeException | if the specified initial size is negative |
---|
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 value 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 |
---|
Clears all of the bits in this BitSet
whose corresponding
bit is set in the specified BitSet
.
set | the BitSet with which to mask this
BitSet |
---|
Returns the number of bits set to true
in this BitSet
.
true
in this BitSet
Sets the bit specified by the index to false
.
bitIndex | the index of the bit to be cleared |
---|
IndexOutOfBoundsException | if the specified index is negative |
---|
Sets all of the bits in this BitSet to false
.
Sets the bits from the specified fromIndex
(inclusive) to the
specified toIndex
(exclusive) to false
.
fromIndex | index of the first bit to be cleared |
---|---|
toIndex | index after the last bit to be cleared |
IndexOutOfBoundsException | if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex |
---|
Cloning this 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.
Compares this object against the specified object.
The result is 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.
obj | the object to compare with |
---|
true
if the objects are the same;
false
otherwiseSets the bit at the specified index to the complement of its current value.
bitIndex | the index of the bit to flip |
---|
IndexOutOfBoundsException | if the specified index is negative |
---|
Sets each bit from the specified fromIndex
(inclusive) to the
specified toIndex
(exclusive) to the complement of its current
value.
fromIndex | index of the first bit to flip |
---|---|
toIndex | index after the last bit to flip |
IndexOutOfBoundsException | if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex |
---|
Returns the value of the bit with the specified index. The value
is 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 |
---|
Returns a new BitSet
composed of bits from this BitSet
from fromIndex
(inclusive) to toIndex
(exclusive).
fromIndex | index of the first bit to include |
---|---|
toIndex | index after the last bit to include |
BitSet
from a range of this BitSet
IndexOutOfBoundsException | if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex |
---|
Returns a hash code value for this bit set. 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,
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 ^= words[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
.
Returns true if the specified BitSet
has any bits set to
true
that are also set to true
in this BitSet
.
set | BitSet to intersect with |
---|
BitSet
intersects
the specified BitSet
Returns true if this BitSet
contains no bits that are set
to true
.
BitSet
is emptyReturns the "logical size" of this BitSet
: the index of
the highest set bit in the BitSet
plus one. Returns zero
if the BitSet
contains no set bits.
BitSet
Returns the index of the first bit that is set to false
that occurs on or after the specified starting index.
fromIndex | the index to start checking from (inclusive) |
---|
IndexOutOfBoundsException | if the specified index is negative |
---|
Returns the index of the first bit that is set to 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:
for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i+1)) {
// operate on index i here
}
fromIndex | the index to start checking from (inclusive) |
---|
-1
if there
is no such bitIndexOutOfBoundsException | if the specified index is negative |
---|
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
value 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 |
---|
Sets the bit at the specified index to the specified value.
bitIndex | a bit index |
---|---|
value | a boolean value to set |
IndexOutOfBoundsException | if the specified index is negative |
---|
Sets the bits from the specified fromIndex
(inclusive) to the
specified toIndex
(exclusive) to the specified value.
fromIndex | index of the first bit to be set |
---|---|
toIndex | index after the last bit to be set |
value | value to set the selected bits to |
IndexOutOfBoundsException | if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex |
---|
Sets the bits from the specified fromIndex
(inclusive) to the
specified toIndex
(exclusive) to true
.
fromIndex | index of the first bit to be set |
---|---|
toIndex | index after the last bit to be set |
IndexOutOfBoundsException | if fromIndex is negative,
or toIndex is negative, or fromIndex is
larger than toIndex |
---|
Sets the bit at the specified index to true
.
bitIndex | a bit index |
---|
IndexOutOfBoundsException | if the specified index is negative |
---|
Returns the number of bits of space actually in use by this
BitSet
to represent bit values.
The maximum element in the set is the size - 1st element.
Returns a string representation of this bit set. 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.
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
}".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
value 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 |
---|