java.util
Class BitSet
- Cloneable, Serializable
This class can be thought of in two ways. You can see it as a
vector of bits or as a set of non-negative integers. The name
BitSet is a bit misleading.
It is implemented by a bit vector, but its equally possible to see
it as set of non-negative integer; each integer in the set is
represented by a set bit at the corresponding index. The size of
this structure is determined by the highest integer in the set.
You can union, intersect and build (symmetric) remainders, by
invoking the logical operations and, or, andNot, resp. xor.
This implementation is NOT synchronized against concurrent access from
multiple threads. Specifically, if one thread is reading from a bitset
while another thread is simultaneously modifying it, the results are
undefined.
BitSet()- Create a new empty bit set.
|
BitSet(int nbits)- Create a new empty bit set, with a given size.
|
void | and(BitSet bs)- Performs the logical AND operation on this bit set and the
given
set.
|
void | andNot(BitSet bs)- Performs the logical AND operation on this bit set and the
complement of the given
bs.
|
int | cardinality()- Returns the number of bits set to true.
|
void | clear()- Sets all bits in the set to false.
|
void | clear(int pos)- Removes the integer
pos from this set.
|
void | clear(int from, int to)- Sets the bits between from (inclusive) and to (exclusive) to false.
|
Object | clone()- Create a clone of this bit set, that is an instance of the same
class and contains the same elements.
|
boolean | equals(Object obj)- Returns true if the
obj is a bit set that contains
exactly the same elements as this bit set, otherwise false.
|
void | flip(int index)- Sets the bit at the index to the opposite value.
|
void | flip(int from, int to)- Sets a range of bits to the opposite value.
|
boolean | get(int pos)- Returns true if the integer
bitIndex is in this bit
set, otherwise false.
|
BitSet | get(int from, int to)- Returns a new
BitSet composed of a range of bits from
this one.
|
int | hashCode()- Returns a hash code value for this bit set.
|
boolean | intersects(BitSet set)- Returns true if the specified BitSet and this one share at least one
common true bit.
|
boolean | isEmpty()- Returns true if this set contains no true bits.
|
int | length()- Returns the logical number of bits actually used by this bit
set.
|
int | nextClearBit(int from)- Returns the index of the next false bit, from the specified bit
(inclusive).
|
int | nextSetBit(int from)- Returns the index of the next true bit, from the specified bit
(inclusive).
|
void | or(BitSet bs)- Performs the logical OR operation on this bit set and the
given
set.
|
void | set(int pos)- Add the integer
bitIndex to this set.
|
void | set(int index, boolean value)- Sets the bit at the given index to the specified value.
|
void | set(int from, int to)- Sets the bits between from (inclusive) and to (exclusive) to true.
|
void | set(int from, int to, boolean value)- Sets the bits between from (inclusive) and to (exclusive) to the
specified value.
|
int | size()- Returns the number of bits actually used by this bit set.
|
String | toString()- Returns the string representation of this bit set.
|
void | xor(BitSet bs)- Performs the logical XOR operation on this bit set and the
given
set.
|
clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait |
BitSet
public BitSet()
Create a new empty bit set. All bits are initially false.
BitSet
public BitSet(int nbits)
Create a new empty bit set, with a given size. This
constructor reserves enough space to represent the integers
from 0 to nbits-1.
nbits - the initial size of the bit set
and
public void and(BitSet bs)
Performs the logical AND operation on this bit set and the
given set. This means it builds the intersection
of the two sets. The result is stored into this bit set.
andNot
public void andNot(BitSet bs)
Performs the logical AND operation on this bit set and the
complement of the given bs. This means it
selects every element in the first set, that isn't in the
second set. The result is stored into this bit set and is
effectively the set difference of the two.
cardinality
public int cardinality()
Returns the number of bits set to true.
clear
public void clear()
Sets all bits in the set to false.
clear
public void clear(int pos)
Removes the integer pos from this set. That is
the corresponding bit is cleared. If the index is not in the set,
this method does nothing.
pos - a non-negative integer
clear
public void clear(int from,
int to) Sets the bits between from (inclusive) and to (exclusive) to false.
from - the start range (inclusive)to - the end range (exclusive)
clone
public Object clone()
Create a clone of this bit set, that is an instance of the same
class and contains the same elements. But it doesn't change when
this bit set changes.
- clone in interface Object
- the clone of this object.
equals
public boolean equals(Object obj)
Returns true if the obj is a bit set that contains
exactly the same elements as this bit set, otherwise false.
- equals in interface Object
obj - the object to compare to
- true if obj equals this bit set
flip
public void flip(int index)
Sets the bit at the index to the opposite value.
index - the index of the bit
flip
public void flip(int from,
int to) Sets a range of bits to the opposite value.
from - the low index (inclusive)to - the high index (exclusive)
get
public boolean get(int pos)
Returns true if the integer bitIndex is in this bit
set, otherwise false.
pos - a non-negative integer
- the value of the bit at the specified position
get
public BitSet get(int from,
int to) Returns a new BitSet composed of a range of bits from
this one.
from - the low index (inclusive)to - the high index (exclusive)
hashCode
public int hashCode()
Returns a hash code value for this bit set. The hash code of
two bit sets containing the same integers is identical. The algorithm
used to compute it is as follows:
Suppose the bits in the BitSet were to be stored in an array of
long integers called
bits, in such a manner that
bit
k is set in the BitSet (for non-negative values
of
k) if and only if
((k/64) < bits.length)
&& ((bits[k/64] & (1L << (bit % 64))) != 0)
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 = bits.length-1; i >= 0; i--)
{
h ^= bits[i] * (i + 1);
}
return (int)((h >> 32) ^ h);
}
Note that the hash code values changes, if the set is changed.
- hashCode in interface Object
- the hash code value for this bit set.
intersects
public boolean intersects(BitSet set)
Returns true if the specified BitSet and this one share at least one
common true bit.
set - the set to check for intersection
- true if the sets intersect
isEmpty
public boolean isEmpty()
Returns true if this set contains no true bits.
- true if all bits are false
length
public int length()
Returns the logical number of bits actually used by this bit
set. It returns the index of the highest set bit plus one.
Note that this method doesn't return the number of set bits.
- the index of the highest set bit plus one.
nextClearBit
public int nextClearBit(int from)
Returns the index of the next false bit, from the specified bit
(inclusive).
from - the start location
nextSetBit
public int nextSetBit(int from)
Returns the index of the next true bit, from the specified bit
(inclusive). If there is none, -1 is returned. You can iterate over
all true bits with this loop:
for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i + 1))
{
// operate on i here
}
from - the start location
- the first true bit, or -1
or
public void or(BitSet bs)
Performs the logical OR operation on this bit set and the
given set. This means it builds the union
of the two sets. The result is stored into this bit set, which
grows as necessary.
set
public void set(int pos)
Add the integer bitIndex to this set. That is
the corresponding bit is set to true. If the index was already in
the set, this method does nothing. The size of this structure
is automatically increased as necessary.
pos - a non-negative integer.
set
public void set(int index,
boolean value) Sets the bit at the given index to the specified value. The size of
this structure is automatically increased as necessary.
index - the position to setvalue - the value to set it to
set
public void set(int from,
int to) Sets the bits between from (inclusive) and to (exclusive) to true.
from - the start range (inclusive)to - the end range (exclusive)
set
public void set(int from,
int to,
boolean value) Sets the bits between from (inclusive) and to (exclusive) to the
specified value.
from - the start range (inclusive)to - the end range (exclusive)value - the value to set it to
size
public int size()
Returns the number of bits actually used by this bit set. Note
that this method doesn't return the number of set bits, and that
future requests for larger bits will make this automatically grow.
- the number of bits currently used.
toString
public String toString()
Returns the string representation of this bit set. This
consists of a comma separated list of the integers in this set
surrounded by curly braces. There is a space after each comma.
A sample string is thus "{1, 3, 53}".
- toString in interface Object
- the string representation.
xor
public void xor(BitSet bs)
Performs the logical XOR operation on this bit set and the
given set. This means it builds the symmetric
remainder of the two sets (the elements that are in one set,
but not in the other). The result is stored into this bit set,
which grows as necessary.
BitSet.java -- A vector of bits.
Copyright (C) 1998, 1999, 2000, 2001, 2004, 2005 Free Software Foundation, Inc.
This file is part of GNU Classpath.
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